Temperature Cycling Conditions Research Articles

Damage based PoF model of solder joints under temperature cycling and electric coupling condition

To predict the life of solder joints under temperature cycling and electric coupling condition, this paper proposes a Physics of Failure (PoF) model based on the continuum damage mechanics (CDM). Firstly, considering the effect of current on solder's mechanical properties, the current-affected constitutive models of plastic fatigue and creep are constructed. Then, based on the mechanism of energy dissipation, a unified creep-plasticity damage evolution law is deduced, and the nonlinear accumulation damage model is developed. Choosing electric resistance as the indirect damage variable measure, the thermal-electric coupling PoF model is finally established by substituting the current-affected constitutive models into the damage evolution model. A thermal-electric coupling test is carried out to verify the accuracy of PoF model. The experimental results confirm that the proposed PoF model can effectively predict the life of solder joints under temperature cycling and electric coupling condition.

Long Cycle Stability of Conversion Metal Fluoride Cathodes in Polymer Electrolytes

The development of Li-ion batteries (LIBs) has been slowed down to a mere 1-2% per year. The skyrocketing price of Co (>30 $USD kg-1) and Ni (>15 $USD kg-1), their limited resources, and accompanying to that low energy density of intercalation-chemistry batteries make it difficult the pack cost to fall to $90-100 kWh-1 or even below. The improvements in LIB energy density (> 1.0 kWh/L) at a reduced cost (<$50-70 kWh-1) can be sought from conversion metal fluoride cathodes (FeF2(3), CuF2 or MFx), which exhibit 2-3 times higher energy density (in Si-/Li-anodes based cells) and low cost (6-9 USD cents for Fe and 6-7 $USD fro Cu per kg, respectively). To streamline these battery chemistries, intrinsically poor ionic conductivity of MFx, substantial volume (up to 30%) and morphological changes during cycling, active material dissolution, substantial resistance buildup, and irreversible growth of the cathode electrolyte interphase (CEI) need to be minimized. By utilizing strong and tough ionically conducting polymer electrolyte matrix and elevated temperature cycling conditions (50 °C), we demonstrated formation of thin conformal CEI, substantial mechanical resilience, decreased internal resistance, reducing of active material dissolution, and overall improvement in performance of FeF2 to 300 cycles at ~400 mAh g-1. Figure 1

Experimental study on the influence of temperature cycle on low-rank coal permeability

The formation temperature is a key factor affecting coalbed methane (CBM) migration in reservoirs. Both the prediction of CBM production and prevention of mine gas disasters require the understanding on the controlling mechanism of temperature on coal permeability. We experimentally examined the evolution of permeability for natural low-rank coal samples under various stresses and cyclic temperature conditions. Apparent permeability and intrinsic permeability decrease significantly when the temperature increases and they only partially recover after the temperature returns. The permeability loss decreases greatly with the increasing number of temperature cycles. The permeability loss due to the rising temperature and the irreversible permeability loss for a whole temperature cycle decrease prominently with increasing confining stress. The impacts of swelling/shrinking of coal matrix, roughness of surface, pore compressibility and weakly bound water in coal on temperature sensitivity of coal permeability are investigated.

Enhancement of the Unified Constitutive Model for Viscoplastic Solders in Wide Strain Rate and Temperature Ranges

Eutectic 63Sn-37Pb solder is a typical viscoplastic material widely used in aerospace applications. In order to benchmark the mechanical reliability of electronic packaging structures in harsh environments, this study focused on the constitutive behavior of the solder. A unified creep-plasticity constitutive model is proposed with an enriched flow rule to satisfactorily describe the plastic and hardening stages. The strain rate range of 10-4 and 10-2 s-1 and the temperature range of -55 and 125°C are covered by a series of comprehensive uniaxial tensile experiments. Moreover, the experimental results are analyzed to elucidate the underlying mechanism of the calibrated parameters. It is found that the drag strength increases with temperature, while its slope is reduced with the strain rate. The short range of back stress is closely associated with temperature to influence the hardening slope of the stress–strain relationships. The value of hardening exponent is sensitive to strain rate and thus determined to be 0.52 and 2.72 for the strain rate greater and less than 2·10-4 s-1, respectively. The strain rate and temperature ranges in this study are capable of covering the temperature cycling tests for reliability qualification of electronic devices. Thus, the proposed enhancement of the unified creep-plasticity constitutive model facilitates the finite element simulations of packaging structures under temperature cycling conditions. This framework of the proposed constitutive model is readily extended to other types of viscoplastic solders within wide strain rate and temperature ranges.

Analyzing and Eliminating Die Passivation Crack in a Power Leadframe Package using Submodeling Approach

This paper presents the submodeling approach in thermo-mechanical simulation of the die passivation crack encountered in a power leadframe package subjected to temperature cycling condition. Without using modeling and simulation in resolving semiconductor package development issues, the process would be very costly and time-consuming. For die passivation crack, the details of the different layers of the die passivation need to be modeled and this would result in a large simulation model with considerable solution time. However, a technique known as submodeling can be used to reduce solution time without sacrificing accuracy of results. In this study, submodeling was successfully used to analyze the stresses in the critical passivation layer that resulted in the best design that eliminated the passivation crack. The modeling result showed that the crack could be eliminated by using the right passivation material layer combination and thickness. An increase in the thickness of the material layers and the additional of sublayers have provided significant stress reduction in the topmost critical passivation layer resulting in crack elimination.

Interaction of thermal cycling and electric current on reliability of solder joints in different solder balls

This paper deals with the effects of electric current on the thermomechanical lifetime of solder joint as the most vulnerable part in electronic packages. The main focus of this paper is located on the Sn3.8Ag-0.5Cu based solder. Different current densities from 1 A mm−2 to 10 A mm−2 are under considered in two well-known solder ball joints, namely barrel- and hourglass-type, in the temperature cycling conditions. Electrical properties of the interested solder joints are experimentally extracted and applied to the finite element analysis in order to reveal the thermomechanical coupling effects of thermal cycling and electric current. Two most important phenomena including joule heating effects and induced triaxility play major roles in determination of solder joint types in the electronic packages. The results reveal that at the lower current density in which the joule heating effects are insignificant, the sharp triaxiality in the barrel-type solder joint is evident due to sharp tilting angle of solder joint. However, in the higher current densities in which the joule heating effects come into play, the number of cycle to failure of hourglass-type solder joint is lower in comparison with barrel-type solder joint. This event may be due to the lower diameter of hourglass-type solder joint in its neck so that more losses in the neck of hourglass-type solder joint, the more effective joule heating is occurred.

Effect of nanostructured reinforcement of adhesive on thermal cycling performance of a single-lap joint with composite adherends

Nanostructure of adhesive increased the failure load of bonded joints. Adhesively bonded joints are often exposed to alternating warm and cold temperatures in many applications. Hence investigation of their thermal cycle performance is very important. In the present study, the tensile strength of adhesively bonded single lap composite joints (SLCJs) was experimentally investigated under ambient temperature and thermal cycling conditions. In the study, carbon fiber fabric reinforced (CFFR) composites (0/90°) with Plain Weave (PW) were used as the adherend; DP460 tough and DP125 flexible adhesive types were used as the adhesive and 1 wt% Graphene-COOH, Carbon Nanotube-COOH and Fullerene C60 were used as the nanostructures. Six different thermal cycles were applied to SLCJs and their tensile failure loads and failure surfaces were investigated. As a result, when the joints obtained through nanostructure non-reinforced adhesives are exposed to thermal cycle, a significant decrease appears in the failure load of the joint. Yet, adding nanostructure to the adhesive enhances the thermal cycle performance of the joint. This enhancement in the thermal cycle resistance changes depending on the structural features of the adhesive, the type of nanostructure and thermal cycle condition.

Temperature stability of oxytocin ampoules labelled for storage at 2°C–8°C and below 25°C: an observational assessment under controlled accelerated and temperature cycling conditions

IntroductionOxytocin, administered via injection, is recommended by WHO for the prevention and treatment of postpartum haemorrhage. However, the susceptibility of oxytocin injection to thermal degradation has led WHO and UNICEF...

Modeling the Interdependences Between Voltage Fluctuation and BTI Aging

With technology scaling, the susceptibility of circuits to different reliability degradations is steadily increasing. Aging in transistors due to bias temperature instability (BTI) and voltage fluctuation in the power delivery network of circuits due to IR-drops are the most prominent. In this paper, we are reporting for the first time that there are interdependences between voltage fluctuation and BTI aging that are nonnegligible. Modeling and investigating the joint impact of voltage fluctuation and BTI aging on the delay of circuits, while remaining compatible with the existing standard design flow, is indispensable in order to answer the vital question, “what is an efficient (i.e., small, yet sufficient) timing guardband to sustain the reliability of circuit for the projected lifetime?” This is, concisely, the key goal of this paper. Achieving that would not be possible without employing a physics-based BTI model that precisely describes the underlying generation and recovery mechanisms of defects under arbitrary stress waveforms. For this purpose, our model is validated against varied semiconductor measurements covering a wide range of voltage, temperature, frequency, and duty cycle conditions. To bring reliability awareness to existing EDA tool flows, we create standard cell libraries that contain the delay information of cells under the joint impact of aging and IR-drop. Our libraries can be directly deployed within the standard design flow because they are compatible with existing commercial tools (e.g., Synopsys and Cadence). Hence, designers can leverage the mature algorithms of these tools to accurately estimate the required timing guardbands for any circuit despite its complexity. Our investigation demonstrates that considering aging and IR-drop effects independently , as done in the state of the art, leads to employing insufficient and thus unreliable guardbands because of the nonnegligible (on average 15% and up to 25%) underestimations. Importantly, considering interdependences between aging and IR-drop does not only allow correct guardband estimations, but it also results in employing more efficient guardbands.

Experimental and numerical determination of the thermal cycle performance of joints obtained with nanostructure-doped nanocomposite adhesives

Particularly findings from nanoscience influence materials and mechanical sciences deeply as well as other disciplines. Polymers containing nanostructures attracted attention as nanocomposite materials. This study involves the production of a new nano adhesive utilizing the advantageous parameters of carbon-nano-reinforced polymers used for adhesively bonded, particularly in aerospace applications, and the mechanical and thermal cycle performance of this new product. In this study, the tensile mechanical properties of single-lap joints (SLJs), which are the most widely used type of adhesive joint geometry, obtained by adding nano-particle to adhesive was investigated experimentally and numerically under ambient temperature and thermal cycle conditions. The experimental results of reinforced adhesive under ambient temperature conditions were taken from open literature. Adhesively bonded SLJs were produced using DP460 tough and DP125 flexible adhesive types as the adhesives; AA2024-T3 aluminum alloy was used as the adherend and 1 wt% Graphene-COOH, Carbon Nanotube-COOH and Fullerene C60 were used as the added nano-particles. The experimental results were compared with the results of numerical calculations that employ Cohesive Zone Model (CZM). Also six different thermal cycle loadings were applied on the SLJs. As a result, when the experimental failure loads were examined, the nanocomposite adhesives obtained by adding nano-particle were found to have increased the thermal cycle resistance of the joints. However, increase rate in the thermal cycle resistance changes depending on the structural features of the adhesive, the type of nano-particle and thermal cycle condition. It was also concluded that the results of numerical calculations matches the experimental results quite satisfactorily.

Multiplex End-Point PCR for the Detection of Three Species of Ophiosphaerella Causing Spring Dead Spot of Bermudagrass.

A multiplex end-point polymerase chain reaction (PCR) assay was developed for identifying the three-fungal species in the genus Ophiosphaerella that cause spring dead spot (SDS), a devastating disease of bermudagrass. These fungi are difficult to identify by morphology because they seldom produce pseudothecia. To achieve species-specific diagnosis, three pairs of primers were designed to identify fungal isolates and detect the pathogen in infected roots. The internal transcribed spacer region, the translation elongation factor 1-α, and the RNA polymerase II second-largest subunit were selected as targets and served as templates for the design of each primer pair. To achieve uniform melting temperatures, three to five random nucleotide extensions (flaps) were added to the 5' terminus of some of the designed specific primers. Temperature cycling conditions and PCR components were standardized to optimize specificity and sensitivity of the multiplex reaction. Primers were tested in multiplex on DNA extracted from axenic fungal cultures and from field-collected infected and uninfected roots. A distinct amplicon was produced for each Ophiosphaerella sp. tested. The DNA from Ophiosphaerella close relatives and other common bermudagrass pathogens did not amplify during the multiplex assay. Metagenomic DNA from infected bermudagrass produced species-specific amplicons while DNA extracted from noninfected roots did not. This multiplex end-point PCR approach is a sensitive and specific molecular technique that allows for correct identification of SDS-associated Ophiosphaerella spp. from field-collected roots.

Retrogradation and Digestibility of Rice Starch Gels: The Joint Effect of Degree of Gelatinization and Storage

Retrogradation affects acceptability of starchy foods; however, it is preferred in some products such as rice noodles. Amylose content, gelatinization temperature, and storage condition were reported to affect retrogradation but with disputed data. The joint effects of these parameters were interested in this study. Rice starch was gelatinized using different temperatures (77, 81, 95, and 121°C) and stored isothermally with temperature cycles for 10 days. Results showed that the most important parameter that affected retrogradation was storage time followed by storage condition and gelatinization temperature. The recrystallization rate constant (k) and Avrami exponent (n) of retrograded starches stored under temperature cycle were higher than isothermal storage. All samples showed similar polymorphs of a mixture of B and V types. High-temperature gelatinized starch gel stored under temperature cycle condition produced higher yield of resistant starch. The study provided useful information on how to apply these parameters to control the retrogradation of starchy foods, especially rice noodle. PRACTICAL APPLICATION: Retrogradation is found to be more prominent at higher gelatinization temperature and longer storage time. Resistant starch produced from retrograded starch depended largely on storage time than storage condition. This finding can be applied to improve rice noodle qualities (by increasing retrogradation) with lower digestibility (by producing higher resistant starch).

Improved Reliability and Mechanical Performance of Ag Microalloyed Sn58Bi Solder Alloys

Ag microalloyed Sn58Bi has been investigated in this study as a Pb-free solder candidate to be used in modern electronics industry in order to cope with the increasing demands for low temperature soldering. Microstructural and mechanical properties of the eutectic Sn58Bi and microalloyed Sn57.6Bi0.4Ag solder alloys were compared. With the addition of Ag microalloy, the tensile strength was improved, and this was attributed to a combination of microstructure refinement and an Ag3Sn precipitation hardening mechanism. However, ductility was slightly deteriorated due to the brittle nature of the Ag3Sn intermetallic compounds (IMCs). Additionally, a board level reliability study of Ag microalloyed Sn58Bi solder joints produced utilizing a surface-mount technology (SMT) process, were assessed under accelerated temperature cycling (ATC) conditions. Results revealed that microalloyed Sn57.6Bi0.4Ag had a higher characteristic lifetime with a narrower failure distribution. This enhanced reliability corresponds with improved bulk mechanical properties. It is postulated that Ag3Sn IMCs are located at the Sn–Bi phase boundaries and suppress the solder microstructure from coarsening during the temperature cycling, hereby extending the time to failure.

Effects of Freeze and Cyclic Load on Impact Resistance of Filling Layer Self-Compacting Concrete (FLSCC)

Filling layer self-compacting concrete (FLSCC) is a key material in newly-built China Rail Track System (CRTS), which is commonly subjected to cyclic dynamic load from high-speed train and various ambient temperature during service. In this paper, a series of indoor simulating experiments was conducted to investigate the impact resistance of FLSCC suffering from cyclic flexural load and different temperature conditions with a Φ75 mm split Hopkinson pressure bar (SHPB). The dynamic increase factors were introduced to evaluate the strain rate effect on various mechanical properties of FLSCC and the corresponding mechanisms were explained. Results show that the dynamic increase factor of compressive strength (DIFc) and peak strain (DIFε) of FLSCC increase linearly with logarithm of strain rate, while specific energy absorption increases exponentially with strain rate. The impact resistance of FLSCC is greatly influenced by cyclic flexural load and low temperature. The strain rate sensitivity of compressive strength of FLSCC at minus temperature (−20°C) is weaker than that at normal temperature (20°C) and after freeze-cyclic load coupling action the sensitivity decreases further. Similar tendencies were also observed in peak strain and specific energy absorption.

Lifetime Prognosis of Lithium-Ion Batteries Through Novel Accelerated Degradation Measurements and a Combined Gamma Process and Monte Carlo Method

A compositional prognostic-based assessment using the gamma process and Monte Carlo simulation was implemented to monitor the likelihood values of test Lithium-ion batteries on the failure threshold associated with capacity loss. The evaluation of capacity loss for the test LiFePO4 batteries using a novel dual dynamic stress accelerated degradation test, called D2SADT, to simulate a situation when driving an electric vehicle in the city. The Norris and Landzberg reliability model was applied to estimate activation energy of the test batteries. The test results show that the battery capacity always decreased at each measurement time-step during D2SADT to enable the novel test method. The variation of the activation energies for the test batteries indicate that the capacity loss of the test battery operated under certain power and temperature cycling conditions, which can be accelerated when the charge–discharge cycles increase. Moreover, the modeling results show that the gamma process combined with Monte Carlo simulations provides superior accuracy for predicting the lifetimes of the test batteries compared with the baseline lifetime data (i.e., real degradation route and lifetimes). The results presented high prediction quality for the proposed model as the error rates were within 5% and were obtained for all test batteries after a certain quantity of capacity loss, and remained so for at least three predictions.

Probabilistic methodology for reliability assessment of electronic packages

In the mechatronic devices, the finite element analyses are the most used method to determine time-dependent solder joint fatigue response under accelerated temperature cycling conditions, the deterministic analyses are the most used methods. However, the design variables show variability and randomness which will affect the lifetime prediction quality. This paper focuses on solder joint reliability in tape-based chip-scale packages(CSP) with the consideration of uncertainties in material parameters.

The effects of thermal cycle and nanostructure reinforcement on the shear load in adhesively bonded joints

In this study, the shear strength of a nanocomposite adhesive was experimentally and numerically investigated under ambient temperature and thermal cycling conditions. This study used the Thick Adherend Shear Test method, which is commonly used to determine the shear stress–displacement of adhesives. Shear–displacement was determined by an extensometer to accurately compare results obtained from the Thick Adherend Shear Test results for joints with numerical analyses. As a result, when the shear failure load obtained from experiments was examined, the nanocomposite adhesives, obtained by adding a nanostructure into the adhesive, improved both the ambient temperature and thermal cycling performances of the joints.

Experimental Study of Moisture Ingress in First and Second Levels of Electronic Housings

Moisture uptake of polymer materials used for electronic packaging and moisture ingress into automotive electronic sensor housings have been studied by exposure to constant and cyclic humidity and temperature conditions. The first-level housing is made of epoxy molding compound (EMC) and encapsulates the sensor silicon-chip. The second-level housing is made of polybutylene terephthalate and contains the EMC attached to a printed circuit board (PCB). The novel approach was to perform in situ measurements of the temperature and the relative humidity (RH) inside the EMC next to the silicon chip, and to measure the humidity transfer from outdoor to the second, and through the first-level housings up to the chip. The effect of the presence of PCB and the self-heating of components have been investigated. The results showed that the time constants for humidity to reach 63% of outdoor conditions are about 2 and 7 days at 60 °C for the second- and first-level housings, respectively. Exposure to cyclic conditions showed that the internal RH tends to reach a steady state, close to the mean value of the cyclic outdoor profile, while the presence of polymeric materials (as PCB) can act as a humidity buffer and absorb and desorb water when subjected to temperature fluctuations.

A simple method for the inhibition of the corrosion of carbon steel by molten nitrate salt for thermal storage in concentrating solar power applications

Corrosion is an important issue in high-temperature applications such as Concentrated Solar Power (CSP) technology, playing a crucial role in the long-term use of storage tanks, heat exchanger and piping materials which account for a considerable component of the investment costs. While there are many studies regarding the corrosion rates of container materials under the conditions of CSP, there is little progress in the field of their degradation prevention by anticorrosion methods. This work presents an analysis of the corrosion mechanisms between the most economical construction material—carbon steel—and molten nitrate salt. A method to protect the carbon steel against corrosion by molten salt at high temperature was proposed, involving the formation of a calcium carbonate layer on the carbon steel surface. The stability of the layer was tested under isothermal and temperature cycling conditions up to 500 °C, in both inert and air atmospheres in the presence or absence of humidity. The protection method proposed has potential to reduce investment costs for CSP technology.

Failure study of Sn37Pb PBGA solder joints using temperature cycling, random vibration and combined temperature cycling and random vibration tests

In this paper, the tin-lead (Sn-37wt%Pb) eutectic solder joints of plastic ball grid array (PBGA) assemblies are tested using temperature cycling, random vibrations, and combined temperature cycling and vibration loading conditions. The fatigue lives, failure modes for the solder joints and the typical locations of the failed solder joints for single-variable loading and combined loading conditions are compared and analyzed. The results show much earlier solder joint failure for combined loading than that for either temperature cycling or pure vibration loading at room temperature. The primary failure mode is cracking within the bulk solder under temperature cycling, whereas the crack propagation path is along the intermetallic compound (IMC) layer for vibration loading. The solder joints subjected to combined loading exhibit both types of failure modes observed for temperature cycling and vibration loading; in addition, cracking through the IMC and the bulk solder is observed in the combined test. For temperature cycling and vibration loading, the components in the central region of the printed circuit board (PCB) have more failed solder joints than other components, whereas for combined loading, the number of failed solder joints in the components in different locations of the PCB is approximately the same.