Power Cycling Test Research Articles

Characterization of high-voltage IGBT module degradations under PWM power cycling test at high ambient temperature

The success of the high temperature power electronic applications depends on the power device reliability. The increasing thermal demands, like in hybrid electric cars, require power devices operating at junction temperatures above their common level of 125 °C. The thermal cycles generated in standard modules in such conditions induce several failure mechanisms in their package and chips. This article presents ageing tests of an EconoPIM IGBT module submitted to PWM power cycling at high ambient temperature. Several electrical and thermal parameters are monitored to detect failure onsets in the module components. Static and dynamic measurements are periodically made to reveal possible module characteristic drifts, and to better understand the effects of this kind of cycling test on the module static and switching behaviors. The follow-up of the dynamic parameter evolution represents the originality of this study.

Accelerated mechanical fatigue testing and lifetime of interconnects in microelectronics

Due to the rapid development of packaging industry accelerated reliability testing for evaluation of lifetime of electronic components are increasingly utilized. In addition to common active thermal cycling procedures, accelerated mechanical fatigue testing provides a new possibility to assess the reliability of microelectronic components, mainly due to the significantly shorter duration of testing time. In this investigation we have used an ultrasonic fatigue testing system in combination with a special experimental set-up for qualification and lifetime determination of microelectronic interconnects. Using this technique, fatigue life of Al wire bonded interconnects were determined and S-N curves (shear stress as a function of loading cycles) up to N=109 were plotted. Three dimensional elasto-plastic FEM simulations were performed to determine the distributions of shear stress and plastic strain generated during cyclic fatigue in the bond area. Furthermore, the FEM model was employed to predict the lifetime of wire-bonds. The results were correlated to the lifetime curves of similar bonds obtained by power cycling tests. Detailed microstructural investigations were performed by means of EBSD -SEM to study the evolution of microstructure of the interconnects subjected to thermal and mechanical fatigue loading. This study demonstrates the applicability of accelerated mechanical fatigue testing as an alternative to time consuming thermal cycling for qualification of microelectronic interconnects.

Accelerated Tests for the Effects of Power Cycling on Tantalum Capacitors in a Humid Environment

Power cycling may occur in electrical devices used in the field, and it may often take place in a humid environment with high temperature, further accelerating stress effects. This study focuses on testing the effects of power cycling; especially the effects of a single off period on surface mount tantalum capacitors in a humid environment. First, the effects of temperature and humidity on tantalum capacitors are introduced. Research was done by using the standard 85/85 test and new kind of power cycling tests that were developed based on the 85/85 test. These new tests were done in 85/85 conditions, with a single power off period of 70 h in the beginning of a test or in the middle of a test. Also, the moisture absorption of tantalum capacitors was examined. The moisture absorption results show that when the devices are off, they absorb moisture faster than when they are on. The accelerated test results suggest that humidity is absorbed during a high humidity/high temperature test, especially during the off period, and catastrophic failures occur when devices are turned on afterward. The new kind of reliability tests that were developed on the basis of the standard 85/85 test could be efficiently used for examining the effects of power cycling in a humid environment.

The Development and Reliability of a Repeated Anaerobic Cycling Test in Female Ice Hockey Players

The purpose of this study was to develop and assess the reliability of a repeated anaerobic power cycling test designed to mimic the repeated sprinting nature of the sport of ice hockey. Nineteen female varsity ice hockey players (mean X +/- SD age, height and body mass = 21 +/- 2 yr, 166.6 +/- 6.3 cm and 62.3 +/- 7.3) completed 3 trials of a repeated anaerobic power test on a Monark cycle ergometer on different days. The test consisted of "all-out" cycling for 5 seconds separated by 10 seconds of low-intensity cycling, repeated 4 times. The relative load factor used for the resistance setting was equal to 0.095 kg per kilogram body mass. There was no significant difference between the peak 5-second power output (PO), mean PO, or the fatigue index (%) among the 3 different trials. The peak 5-second PO was 702.6 +/- 114.8 w and 11.3 +/- 1.1 w x kg, whereas the mean PO across the 4 repeats was 647.1 +/- 96.3 w and 10.4 +/- 1.0 w x kg averaged for the 3 different tests. The fatigue index averaged 17.8 +/- 6.5%. The intraclass correlation coefficient for peak 5-second, mean PO, and fatigue index was 0.82, 0.86, and 0.82, respectively. This study reports the methodology of a repeated anaerobic power cycling test that was reliable for the measurement of PO and calculated fatigue index in varsity women ice hockey players and can be used as a laboratory-based assessment of repeated anaerobic fitness.

Using In situ Capacitance Measurements to Monitor the Stability of Thermal Interface Materials in Complex PCB Assemblies

A thermal solution for an array of voltage transformer modules which are cooled by a large area, common aluminum heat spreader for a high end server was evaluated using an in situ, capacitive bond line thermal measurement technique. The method measures the capacitance of a non-electrically conducting thermal interface material (TIM) between the electronic module and heat spreader to quantify the TIM bond line effective thickness during assembly and operation. The thermal resistance of the TIM has the same geometric dependence as the inverse of capacitance, therefore, the capacitive technique also provided a monitor of the thermal performance of the interface. This technique was applied to measure the bond line in real time during the assembly of the heat spreader to an array of 37 modules mounted on a printed circuit board. The results showed that the target bond lines were not achieved by application of a constant force alone on the heat spreader, and guided an improved assembly process. The mechanical motion of the TIM was monitored in situ during thermal cycling and found to fluctuate systematically from the hot to cold portions of the thermal cycle, either compressing or stretching the TIM respectively. The capacitive bond line trend showed thermal interface degradation vs. cycle count for several modules which was confirmed by disassembly and visual inspection. Areas of depleted TIM ranged as high as 25% of the module area. Several design and material changes were shown to improve the TIM stability. Power cycling tests were run in parallel to the thermal cycle tests to help relate the results to field performance. The capacitance technique enabled the development and verification of a thermal solution for a complex mechanical system early in the development cycle.

Evaluation of Fatigue Life of Semiconductor Power Device by Power Cycle Test and Thermal Cycle Test Using Finite Element Analysis

To accurately predict the fatigue life of a power device, a fatigue life evaluation method that is based on the power cycle is presented in terms of an algorithm based on a combination of electrical analysis, heat analysis, and stress analysis. In literature, the fatigue life of power devices has been evaluated on the basis of the thermal cycle. This cycle is alternately repeated within a range from a high temperature to a low temperature. In an actual operating environment, however, a power device works in a power cycle that consists of being switched ON and OFF. To accurately predict the fatigue life cycle of a device, then, the evaluation should take account of this important aspect of the power cycle. To verify the utility of the evaluation method presented in this study, the results for a power cycle based on the combined use of electrical analysis, heat analysis, and stress analysis are compared to the results based on the thermal cycle, as found in the literature. Our conclusion is that the fatigue life cycle as estimated by the thermal cycle test is higher than that estimated by the power cycle.

Impact of Calendar Life and Cycling Ageing on Supercapacitor Performance

Supercapacitors (SCs), which are also known as ultracapacitors, are commonly based on porous activated carbon electrodes and electrostatic charge-storage mechanisms. Carbon electrodes are supposed to be chemically and electrochemically inert, and the electrostatic nature of the charge-storage mechanism is highly reversible. These properties should assure that SCs have an infinite shelf life. However, in practice, SC cells exhibit performance fading when they are used for months. The purpose of this paper is to compare the performance fading of SCs in two types of tests. The first accelerated test is the calendar life test, which evaluates cell degradation when cells are used at elevated voltages and temperatures; these degradations are observed in cells during rest periods. The second test is the power cycling test, which corresponds to degradations during the actual use of SCs as peak power sources in hybrid electric applications. In this paper, we use an impedance model to monitor changes in cell behavior. This analytical impedance model is based not only on physical quantities, such as double-layer capacitance, specific area, and electrolyte conductivity, but on elementary electrode dispersion as well. This model is validated in the frequency domain using the initial state of the tested SC for different temperature and voltage configurations. Then, we present and specify two types of tests. A periodic characterization based on impedance spectroscopy is done to quantify impedance changes during the ageing tests. The obtained results confirm that the impedance real part is increasing and that the capacitance is decreasing during the two ageing tests; however, the way they change is different. Indeed, the shape of the impedance real part is conserved in the calendar life test, whereas it is distorted in the power cycling test. This difference will be explained in terms of the evolution of the impedance model parameters. This paper confirms that the two ageing tests affect the SC performances differently.

Accelerated active ageing test on SiC JFETs power module with silver joining technology for high temperature application

This paper presents the accelerated active power cycling test (APCT) results on SiC JFETs power module dedicated to operate at high temperature. This study partly focuses on the new chip joining technology (LTJT), which permit to use SiC JFETs transistors at higher temperatures. We present the different die attachments tested with high temperature lead solder and silver sintering joining technologies. Active power cycling results for high junction temperature T jmax = 175 °C with Δ T j = 80 K to perform an evaluation of main damages during active test are carried out and a comparison between lead and silver chip joining technologies is presented.

Analysis of the dynamic behavior changes of supercapacitors during calendar life test under several voltages and temperatures conditions

Supercapacitors, also known as ultracapacitors are based on porous activated carbon electrodes and on electrostatic charge storage mechanisms. Carbon electrodes are supposed to be chemically and electrochemically inert and the electrostatic nature of the charge storage mechanism is highly reversible. These properties should assure that supercapacitors have an infinite shelf life. But in practice, supercapacitor cells exhibit performances fading when they are used for months. The purpose of this paper is to evaluate the performances fading of supercapacitors during calendar life test which correspond to lower current solicitations than power cycling test. In case of hybrid electric vehicle, which is a key application of ultracapacitors, this ageing test is useful because long rest periods represent a significant time of the vehicle real use. The degradation method of calendar life tests consists in maintaining the cells at high voltage and temperature. A periodic characterization based on impedance spectroscopy is done in order to quantify impedance changes. The obtained results confirm that impedance real part is increasing and the capacitance is decreasing.

Reliability of Lead-Free Solder Interconnections in Thermal and Power Cycling Tests

Lead-free solder interconnection reliability of thin fine-pitch ball grid array (BGA) lead-free packages has been studied experimentally as well as with finite-element (FE) simulations. The reliability tests were composed of the thermal shock test, the local thermal cycling test (resistors embedded in the board around the package), and the power cycling test (heat generation in the die). A 3-D board-level finite-element analysis (FEA) with local models was carried out to estimate the reliability of the solder interconnections under various test conditions. Due to the transient nature of the local thermal cycling test and the power cycling test, a sequential thermal-structural coupling analysis was employed to simulate the transient temperature distribution as well as the mechanical responses. Darveaux's approach was used to predict the life time of the solder interconnections. Furthermore, the numerical results validated by the experimental results indicated that the diagonal solder interconnections beneath the die edge were the most critical ones of all the tests studied here. It has been found that the fatigue life in the power cycling test was much longer than that in the other two tests. Detailed discussions about the failure mechanism of solder interconnections as well as the microstructural observations of the primary cracks are reported in this paper.

Experimental investigation on operating instability of a dual compensation chamber loop heat pipe

The operating instability of a dual compensation chamber loop heat pipe (DCC-LHP) including temperature hysteresis, reverse flow and temperature oscillation is described and explained in this paper. Test results indicate that the steady state operating temperature under the variable conductance mode is not the same during the power cycle tests with the same heat load, and it is lower during the power reduction cycle than that during the power increase cycle. Orientation has an effect on the heat load range when temperature hysteresis occurs, and the effect of power variation amplitude can be ignored. Reverse flow tends to occur in some of the startups at low heat loads, even if vapor existed in the vapor grooves initially, which is caused by a higher pressure inside the wick due to evaporation in the evaporator core or vapor penetration into it. Temperature oscillation tends to occur in some of the startups at low head loads or some steady-state operations at high heat loads. Especially when the compensation chamber with the bayonet through is above the evaporator, the incidence rate of temperature oscillation is high.

Coupled Power and Thermal Cycling Reliability of Board-Level Package-on-Package Stacking Assembly

In this paper, the sequential thermal-mechanical coupling analysis, which solves in turn the transient temperature field and subsequent thermomechanical deformations, is performed to investigate thermal characteristics along with fatigue reliability of a board-level package-on-package (PoP) stacking assembly under coupled power and thermal cycling test conditions. Effects of powering sequences on thermal characteristics and fatigue reliability of the PoP are examined. The numerical analysis shows that coupled power and thermal cycling creates temperature excursions based on the thermal cycling profile. Also, reliability of the PoP is highly related to the range of temperature excursions and the degree of deviation of the temperature profile from the thermal cycling profile.

A fast mechanical test technique for life time estimation of micro-joints

Abstract A novel accelerated mechanical testing method for reliability assessment of micro-joints in the electronic devices is presented as an alternative to time consuming thermal and power cycling test procedures. A special experimental set-up in combination with an ultrasonic resonance fatigue testing system and a laser Doppler vibrometer is used to obtain fatigue life curves of micro-joints under shear loading. Using this method fatigue life curves of Al wire bonded micro-joints were obtained up to 10 9 number of loading cycles and discussed with regard to micro-mechanisms of the bond failure. Failure analysis of the fatigued micro-joints showed that the predominant failure mechanism of power cycling tests, bond wire lift-off, was reproduced by the mechanical testing procedure. Life time of the micro-joints was modelled using a Coffin–Manson type relationship and showed a good correlation to life time curves obtained by power cycling tests. The major advantage of the proposed fast mechanical testing method is the significant reduction of the testing time in comparison with conventional thermal and power cycling tests. Furthermore subsequent examination of the failure surface provides a reliable tool for improvement of the bonding process. The proposed high frequency fatigue testing system can be applied as a rapid qualification and screening tool for various kinds of interconnects in electronic packaging.

Comparison between changes of ultracapacitors model parameters during calendar life and power cycling ageing tests

This paper deals with the performances fading of ultracapacitors under calendar life and power cycling tests. The used impedance model is analytical and based on physical quantities as double layer capacitance, specific area and electrolyte conductivity but also on elementary electrodes dispersion. This model is validated in frequency domain using the initial state of the tested ultracapacitor. Then, the two types of tests are presented and specified. A periodic characterization based on impedance spectroscopy is done in order to quantify the impedance changes during ageing tests. The obtained results confirm that impedance real part is increasing and the capacitance is decreasing during the two ageing tests, nevertheless the way they change is different. Indeed the impedance real part increase is independent of the frequency in calendar life test while, in power cycling test, this increase is accentuated at low frequencies. This difference will be explained thanks to impedance model parameters evolution. This study confirms that the two ageing tests affect differently the ultracapacitor performances.

Thermal Characteristics and Thermomechanical Reliability of Board-Level Stacked-Die Packages Subjected to Coupled Power and Thermal Cycling Test

The sequential thermal-mechanical coupling analysis, which solves in turn the transient temperature field and subsequent thermomechanical deformations, is performed to investigate thermal characteristics along with fatigue reliability of a board-level stacked-die package under coupled power and thermal cycling test conditions. Different powering conditions and sequences are compared. From the numerical results, we note that under coupled power and thermal cycling tests, reliability performances of a board-level stacked-die package should be similar as long as the total power dissipation prescribed to the package is identical, regardless of how the power distributes among separate dies.

A Study on the Thermal Fatigue Behavior of Solder Joints Under Power Cycling Conditions

Failure mechanisms exposed by environmental accelerating testing methods such as thermal cycling or thermal shock test, may differ from those at service operating conditions. While the device is heated up or cooled down evenly on its external surface during environmental testing, real operating powered devices experience temperature gradients caused by internal local heating, components' different heat dissipation capability, and ambient temperature variation, etc. In this study, a power cycling technique is introduced to better approximate the field operating conditions so as to activate the field failure modes. Power cycling thermal fatigue test is performed with different ball grid array solder joints, that is, lead contained [Sn/37 Pb (SP)] and lead free [Sn/4.0Ag/0.5 Cu (SAC)], and the result is compared. In order to account for the thermal fatigue life behavior discrepancy for different solder joint composition, real time Moire interferometry is applied to measure the global/local thermo-mechanical behavior during power cycling excursion. Effective damage parameter, the total average shear strain, is extracted from the experiment and applied to account for the difference in fatigue life result of two different solders. In addition, amount of experimentally measured total average shear strain is mutually verified with finite element method analysis. It is clear that total average shear strain of a solder joint can be an effective damage parameter to predict thermo-mechanical fatigue life. A physical mechanism in terms of thermal material property of solder joints' is proposed to offer some thoughts to abnormal shear strain behavior that leads to discrepancies in fatigue life of two solders. An importance of power cycling testing method is emphasized for certain package designs.

Thermal–Mechanical Coupling Analysis for Coupled Power- and Thermal-Cycling Reliability of Board-Level Electronic Packages

In this paper, we apply the sequential thermal-mechanical coupling analysis that solves, in turn, the transient temperature field and subsequent thermomechanical deformations to investigate thermal characteristics along with fatigue reliability of board-level thin-profile fine-pitch ball-grid-array chip-scale packages under coupled power- and thermal-cycling test conditions. Pure thermal-cycling and pure power-cycling test conditions are also examined and compared. From the comparison of different test conditions, we note that the presence of power cycling leads to significant deviations of junction and mold-top temperatures from the thermal-cycling profile. Nevertheless, for components away from the die, the deviations are less significant. As the power specified to the test vehicle is low, temperature histories on the components induced by coupled power and thermal cycling can be approximated by superposition of the temperature histories induced by pure power cycling and the ones by pure thermal cycling. For the test conditions proposed in this paper, pure power cycling leads to the longest fatigue life among all. For coupled power and thermal cycling, the involvement of power cycling reduces the fatigue life of the test vehicle by about 50% as compared to pure thermal cycling.

Revisiting power cycling test for better life-time prediction in traction

This paper discusses the commonly accepted method for life-time prediction for power converters in traction. The method is based on junction temperature estimation and thermal cycles on a given duty cycle. The predicted numbers of thermal cycles are compared to the curves giving the number of cycles to failure versus temperature cycles. These curves are extrapolated from power cycling tests. Power cycling tests and extrapolation method will be discussed, particularly under the aspect of failure mechanisms that are induced. In order to generate the same failure mechanisms in power cycling than in the real applications, a new power cycling approach is presented.

Monitoring fading rate of ultracapacitors using online characterization during power cycling

This paper deals with the ageing quantification of ultracapacitors in cycle-life tests. Typical micro- and mild-hybrid applications have been used to specify the test profiles in agreement with power requirements. Since ultracapacitors lifetime depends on the temperature, these profiles are adjusted to induce a given self-heating at the beginning of the power cycling tests. Ageing is evaluated thanks to the measurements of the electrical parameters changes. The good reproducibility of the characterization methods has allowed us to monitor the fading rate of ultracapacitors, from two manufacturers, with the proposed current profiles.

Reliability evaluations for board-level chip-scale packages under coupled power and thermal cycling test conditions

To evaluate conjointly the effects of ambient temperature fluctuation and operation bias on the reliability of board-level electronic packages, a coupled power and thermal cycling test has been proposed. In this study, the sequential thermal–mechanical coupling analysis, which solves in turn the transient temperature field and subsequent thermomechanical deformations, is performed to investigate thermal characteristics along with fatigue reliability of board-level thin-profile fine-pitch ball grid array chip-scale packages under coupled power and thermal cycling test conditions. Effects of different power cycling durations are studied. A pure thermal cycling condition is also examined and compared. Numerical results indicate that, for the coupled power and thermal cycling test, a shorter power cycling duration in general leads to a shorter fatigue life. However, the temperature compensation effect elongates the fatigue life under certain power cycling durations.