Thermal Fatigue Life Research Articles

Thermal Fatigue of Ceramics: Theory, Life Predication and Characterization Methods

Thermal fatigue is a common problem when ceramics are used at high temperature. Typically, the mechanic properties of ceramics decrease after either long service times at high temperatures or cycles of temperature changes. The thermal fatigue process, the factors influencing the thermal fatigue and the prediction of the thermal fatigue life of ceramics are concerned topics. The thermal fatigue of ceramics is mainly explained by the critical stress fracture and thermal shock damage theories. The thermal fatigue tests include the traditional strength method, the quench-indentation method and the non-destructive detection such as the acoustic emission technique. Based on the thermal fatigue theories, the thermal fatigue life can be predicted using built models. The establishment of the standards for the testing of ceramic thermal fatigue will enhance the comparability of experimental data and further promote the development of analysis theory of thermal fatigue, benefiting the design of engineering ceramics.

Effect of Carbon Black/Silica Hybrid Filler on Thermal Properties, Fatigue Life, and Natural Weathering of SBR/Recycled NBR Blends

The utilization of nitrile glove waste will spark a great deal of interest in the rubber industry in developing cost-effective techniques to convert waste and used rubber into a processable form. Blends of styrene butadiene rubber/recycled acrylonitrile butadiene rubber (SBR/NBRr) reinforced at 85/15 blend with different ratios of a carbon black/silica (CB/Sil) hybrid filler (50/0, 40/10, 30/20, 20/30, 40/10, 0/50 phr) were tested either with or without the silane coupling agent, Si69. Results showed that the increased thermal stability of blends with Si69 is highly related to the formation of crosslinks between the filler. Thermogravimetric (TG) thermograms showed that the percentage of char residue for blends with Si69 was higher than without Si69. The differential scanning calorimetry (DSC) thermograms of both blends revealed a glass transition temperature (Tg) between 65.0°C and 66.9°C. At all blend ratios, the fatigue life of blends with Si69 was better than blends without Si69. After six months’ exposure to natural weather, blends with Si69 exhibited better tensile properties, retention, and morphology compared to blends without Si69.

PWBにおけるIVHの熱疲労寿命に及ぼすFR-4の積層構造の不均質性の影響（第1報，冷熱サイクル試験と有限要素法解析を用いた寿命の変動要因の検討）

PWBにおけるIVHの熱疲労寿命に及ぼすFR-4の積層構造の不均質性の影響を検討するために，熱疲労寿命に影響する要因を検討する実用的な手法を示し，その手法に基づいて冷熱サイクル試験と有限要素法解析を用いて熱疲労寿命の変動要因を検討した。解析モデルにPWBの平織りのガラスクロスを詳細にモデル化したものを使用することで，解析結果が試験結果のき裂発生状況や故障順序と一致することを確認した。その結果，積層されたガラスクロスの積層状態の違いと，ある積層状態のガラスクロスに対するIVHの形成位置の違いが，IVHの熱疲労寿命に影響していることを示唆した。これらの違いはIVHの熱疲労寿命の変動要因であり，その要因が組み合わさってIVHの熱疲労寿命に影響すると考えられる。

PWBにおけるIVHの熱疲労寿命に及ぼすFR-4の積層構造の不均質性の影響（第2報，変動要因の組み合わせの影響メカニズムとその設計への適用）

PWBにおけるIVHの熱疲労寿命に及ぼすFR-4の積層構造の不均質性の影響（第2報，変動要因の組み合わせの影響メカニズムとその設計への適用）

Reliability Assessment of Preloaded Solder Joint Under Thermal Cycling

The ever increasing power density in modern semiconductor devices requires heat dissipation solution such as heat sink to remove heat away from the device. A compressive loading is usually applied to reduce the interfacial thermal resistance between package and heat sink. In this paper, both experimental approaches and numerical modeling were employed to study the effect of compressive loading on the interconnect reliability under thermal cycling conditions. A special loading fixture which simulated the heat sink was designed to apply compressive loading to the package. The JEDEC standard thermal cycle tests were performed and the resistance of daisy chained circuits was in situ measured. The time to crack initiation and time to permanent failure were identified separately based on in situ resistance measurement results. Failure analysis has been performed to identify the failure modes of solder joint with and without the presence of compressive loading. A finite element based thermal-fatigue life prediction model for SAC305 solder joint under compressive loading was also developed to understand the thermal-fatigue crack behaviors of solder joint and successfully validated with the experimental results.

Research of Fatigue Stress Cracking for Injection Mold Cavity Based on Ansys Workbench

The process of injection molding, packing and cooling for injection mold PET (Polyethylene terephthalate) cavity was analyzed and the cause of fatigue stress cracking was investigated. An analysis method of injection mold cavity fatigue based on Ansys Workbench(AWB)was put forward. A simulation of temperature field, displacement, thermal stress field and fatigue life for the cavity of a work cycle based on heat transfer theory was completed. Provide effective measures to avoid fatigue stress cracking and optimization design of the injection mold.

A Thermal Fatigue Life Prediction Method of Aluminum Alloy Piston in Material Application Engineering

In this paper, based on the Manson-Coffin fatigue theory, a thermal fatigue life prediction method for aluminum alloy engine piston is established, by introducing the nonlinear functions between the fatigue strength coefficient, fatigue continuation coefficient and elastic modulus with temperature. Compared with the results from the linear elastic model and the linear plastic model application, this nonlinear thermal fatigue life prediction method’s results fit much better to the experimental results, which means that this method is more accurate and credible than the other models.

Estimation and visualization of the fatigue life of Pb-free SAC solder bump joints under thermal cycling

A method for estimating the fatigue life of Pb-free solder (Sn–3.0Ag–0.5Cu) bump joints under thermal cycling is described. The test specimens were 4, 6 and 8mm chip size packages mounted on printed circuit boards. To develop a semi-analytical model for estimating the thermal fatigue life, thermal cycle tests were carried out on the test specimens and the thermal fatigue life obtained experimentally was compared with the corresponding result from nonlinear, elastic–plastic finite element analysis. It was found that the chip size affected the thermal fatigue life and the strain accumulated in the solder bumps during thermal cycling. This was due to the difference in mechanical boundary conditions around the Si chip. Based on the Coffin–Manson law, an equation for estimating the thermal fatigue life was derived and the predicted fatigue life for various chip sizes and under different rises in temperature were found to be in good agreement with the experimental results. Moreover, a measurable parameter that correlates with the accumulated strain in the solder bumps was introduced for estimating the thermal fatigue life of the test specimens.

Thermal Fatigue Characteristics of Die Attach Materials for Packaged High-Brightness LEDs

With the increase of driving current and power density, the thermal fatigue characteristics of die attach materials have become an important issue impacting the long-term reliability of high-brightness light-emitting diodes (HB LEDs). In this paper, an accelerated power cycling method is used to predict the thermal fatigue life of die attach materials for packaged HB LEDs. The thermal fatigue life of Au80Sn20 eutectic and silver paste is investigated at driving currents of 650, 675, and 700 mA. Changes in the thermal resistance of die attach materials are monitored by the noninvasive structure function method based on the measurement of transient temperature response curves through power cycling experiments. Results of C-mode scanning acoustic microscopy and cross-sectional scanning electron microscopy indicate that delamination is the main failure mechanism of the die attach materials under thermal fatigue stress. Furthermore, the thermal fatigue life of die attach materials can be derived from the relationship between lifetime and temperature difference according to the Coffin-Manson relationship. The results suggest that Au80Sn20 eutectic possesses a longer thermal fatigue life than silver paste at the same temperature difference of thermal fatigue stress.

Characterization of IMC layer and its effect on thermomechanical fatigue life of Sn–3.8Ag–0.7Cu solder joints

Intermetallic compound (IMC) growth was investigated under isothermal aging condition at 125°C for up to 500h. The evolution in the IMC morphology and microstructure were observed at four aging time conditions for 0, 120, 260 and 500h, respectively. Solid state IMC growth thickness measurements were determined from scanning electron microscope (SEM) observations for Cu–Sn and Cu–Ni–Sn IMC systems. The Young’s modulus and hardness of the IMCs were determined by nanoindentation tests. A finite element analysis (FEA) was carried out to model the effect of the IMC layer on the solder joint thermal fatigue life. The nanoindentation mechanical properties of Cu6Sn5 and CuNiSn IMCs were modeled with different IMC thicknesses in the FEA simulation to study the effect of the IMC growth on the fatigue life of the solder joint. It was shown that the IMC layer reduces the fatigue life of the solder joints and thick IMC layer results in a lower fatigue life. In addition, thermal cycling test and analysis for plastic ball grid array (PBGA) package with Sn–3.8Ag–0.7Cu Pb-free solder joints was performed. The mean-time-to-failure (MTTF) for the PBGA solder joints was determined, which was used for validating the FEA simulation results.

Effects of alloying elements on the thermal fatigue properties of the 15 wt% Cr ferritic stainless steel weld HAZ

We investigated the effects of Nb, W, and V alloying elements on the thermal fatigue properties of the ferritic stainless steel weld heat affected zone (HAZ). Simulation of the weld HAZ and thermal fatigue testing were carried out using a metal thermal cycle simulator (MTCS) under a complete constraint force in the static jig. The fatigue life during cyclic heating and cooling in the temperature range of 200–900°C was strongly related not only to precipitation and coarsening of MX type and Laves precipitates, but also to the Nb content in the solid solution and grain coarsening. The thermal fatigue life increased with Nb and W contents due to the increased amount of (Nb,Ti)(C,N) precipitates and a less coarsened Laves phase, respectively. Contrary to the results with Nb and W additions, there were no obvious effects of V addition.

Reliability of gull-wing and leadless packages subjected to temperature cycling after rework

An experimental study was conducted to determine the effect of rework on the quality and reliability of surface mount solder interconnects. The test vehicle included thin small outline packages (TSOPs) and 2512 resistors assembled onto circuit cards with Sn3.0Ag0.5Cu and Sn63Pb37 solders. The rework process entailed the removal and replacement of the TSOPs and resistors. Reworked assemblies were then subjected to a temperature cycling test. Test results indicated that rework did not degrade the reliability of the TSOP solder attachments, but it decreased the thermal fatigue life of 2512 resistors down by 80% due to the decreased and uneven solder joint heights created by the hand-soldered rework process. Solder interconnect material changes caused by the rework process were not observed to be a significant factor in reliability.

Continuum damage mechanics application in low-cycle thermal fatigue

In this article, a fatigue model for low-cycle thermal fatigue formulated in a continuum damage mechanics framework is presented. The model is based on a unified damage law presented by Lemaitre for low-cycle fatigue, which has been extended to low-cycle thermal fatigue. The temperature dependencies of material parameters are considered in the damage evolution integration to take the non-isothermal condition of loading into account. This model considers the stress triaxiality and non-linearity of damage evolution, and it is developed to a fatigue damage accumulation rule in which the load sequence effect is also included. The stabilized structural response under thermomechanical loading motivates the use of uncoupled analysis approach making the model a fast tool suitable for design purposes in the costly and time-consuming field of thermomechanical fatigue life assessment. To demonstrate the capability and ease of use of this model for real industrial applications, the low-cycle thermal fatigue life of a stainless steel engine exhaust manifold which is in an early stage of design is assessed.

On thermal stress and fatigue life evaluation in work rolls of hot rolling mill

The paper proposes an approach for thermal stress evaluation and fatigue life assessment of work rolls in hot rolling mills. Temperature and thermal stress distributions are calculated with a simplified finite element approach, based on a plane model of work roll loaded on its boundary by rotating thermal actions for a typical hot rolling configuration. A transient of one hour is simulated and the calculated temperature field is next applied as thermal loading in elastic–plastic mechanical simulation, to get thermal stresses and elastic–plastic strains in work roll. Calculated cyclic stresses and strains are finally used to estimate work roll service life, based on Universal Slopes equation that is modified to account for the multiaxial stress state. A comparison of results by three multiaxial fatigue criteria is provided. The obtained results show that, according to such multiaxial criteria, stress multiaxiality would have a great effect on fatigue life, despite it is generally neglected in approaches usually adopted in literature.

Thermo‐mechanical behaviour of DBC substrate assemblies subject to soldering fabrication processes

PurposePower electronics are usually soldered to Al2‐O3 direct‐bond‐copper (DBC) substrates to increase thermal diffusivity, while at the same time increasing electrical isolation. However, soldering gives rise to inherent residual stresses and out‐of‐plane deformation. The purpose of this paper is to look at the effect of soldering processes of Al2‐O3 DBC substrates to copper plates and power electronics, on their thermal fatigue life and warpage.Design/methodology/approachA numerical thermo‐mechanical finite element model, using the Chaboche material model, was developed to identify the thermal plastic strains evolved during soldering of DBC substrates to copper plates and power electronics. The plastic strains in conjunction with established extremely low cycle fatigue life prediction model for ductile material were used to predict the number of soldering cycles to failure. The predicted out‐of‐plane deformation and number of soldering cycles to failures was compared to realistic tests.FindingsSoldering processes drastically reduce the thermal fatigue life of DBC substrates, giving rise to thermal cracking and premature failure. In this study the soldering process considered gave rise to out‐of‐plane deformations, consequently reducing heat dispersion in soldered DBC substrate assemblies. Furthermore, soldering gave rise to interface cracking and failed after three soldering cycles. Numerical finite element models were developed and are in good agreement with the experimental tests results.Research limitations/implicationsThe influence of soldering processes of DBC substrates to copper plates and electronics on the thermal fatigue life should be taken into consideration when establishing the design life of DBC substrates. Finite element models can be utilised to optimize soldering processes and optimize the design of DBC substrates.Originality/valueThe effect of soldering processes on DBC substrates was studied. A numerical finite element model used for the prediction of design life cycle and out‐of‐plane deformation is proposed.

Effects of Corner/Edge Bonding and Underfill Properties on the Thermal Cycling Performance of Lead Free Ball Grid Array Assemblies

Underfilling will almost certainly improve the performance of an area array assembly in drop, vibration, etc. However, depending on the selection of materials, the thermal fatigue life may easily end up worse than without an underfill. This is even more true for lead free than for eutectic SnPb soldered assemblies. If reworkability is required, the bonding of the corners or a larger part of the component edges to the printed circuit board (PCB), without making contact with the solder joints, may offer a more attractive materials selection. A 30 mm flip chip ball grid array (FCBGA) component with SAC305 solder balls was attached to a PCB and tested in thermal cycling with underfills and corner/edge bonding reinforcements. Two corner bond materials and six reworkable and nonreworkable underfills with a variety of mechanical properties were considered. All of the present underfills reduced the thermal cycling performance, while edge bonding improved it by up to 50%. One set of the FCBGAs was assembled with a SnPb paste and underfilled with a soft reworkable underfill. Surprisingly, this improved the thermal cycling performance slightly beyond that of the nonunderfilled assemblies, providing up to three times better life than for those assembled with a SAC305 paste.

Thermal Fatigue Analysis of the Engine Exhaust Manifold

Exhaust manifold is the main heated part of the engine, which bears the alternating heat loads and vibration loads in the process of high speed rotation in the extremely bad working environment. According to the method of fluid-solid coupling, the temperature, stress, strain and failure process of the exhaust manifold is reproduced through Abaqus finite element analysis and practical fatigue failure analysis. Comparing the simulation results with the real situation, it is proved that the finite element model is reasonable and the solving conditions are accurate. The further study of the problem will provide theoretical basis for the subsequent materials and structure optimization of the exhaust manifold, which will have important reference for the thermal fatigue damage, life prediction and control under the high temperature and thermal shock.

Thermal fatigue striping damage assessment from simple screening criterion to spectrum loading approach

Thermal fatigue is an important degradation mechanism for the life time assessment of nuclear reactor components. A reliable life-assessment of components is difficult because usually only the nominal temperature differences are known and the thermal surface loadings are not known. This paper outlines a multi-level procedure for assessment of pipe components subjected to thermal fatigue. The different levels are: (a) simple screening criterion, (b) the thermal spectrum replaced by a sinusoidal load (SIN-method) with constant amplitude and frequency and assessment of crack initiation and crack propagation in relation to a critical frequency, and (c) spectrum loading applied to crack initiation and propagation. The different levels are described together with the underlying assumptions. The different levels in the procedure are applied to assess the life of the Civaux case, where a pipe failed due to thermal fatigue. The different levels of the procedure give conservative estimates of the thermal fatigue life but where the conservatism is reduced with the more complex higher level assessments. The influence of important factors such as boundary conditions and primary loads are illustrated. It is also shown that the SIN-method can be used to determine a threshold below which there is no thermal fatigue failure.

Study on Thermal Fatigue Life Prediction of Cylinder Head

Thermal fatigue tests were conducted on diesel engine cylinder heads of gray cast iron HT250 with conductive heating fatigue test rig. The thermal fatigue life is affected by the maximum temperature and heating time. The relationship between thermal fatigue life, temperature, and heating time was researched. Thermal fatigue life prediction model was derived from classical energy fatigue criteria. The parameters of the model were obtained from the results of the thermal fatigue test. The model and thermal fatigue test method are suitable for cylinder heads of cast irons and cast aluminum alloys, the parameters should be fixed by thermal fatigue test.

F603 インバータ基板のはんだ接合部の熱疲労寿命の評価 : 応力特異性パラメータを用いた評価(F6.企業におけるCAE活用,フォーラム)

It is well known that thermal fatigue easily occurs in the solder joints of inverter circuit board. In this study, we tried to evaluate thermal fatigue life of solder joints with the stress singularity parameters near the solder joint edges. Firstly, we made constitutive equations of the solder materials and confirmed its precision. Next, using FEM analyses, we calculated stress singularity parameters near the solder joint edges for power modules under the conditions of thermal cycle experiments and power cycle experiments. Finally, we made evaluation equations of thermal fatigue life for solder joints by connecting stress singularity parameters and experiment results with fatigue laws.