Showing papers by "Michael Pecht published in 2009"

Precursor Parameter Identification for Insulated Gate Bipolar Transistor (IGBT) Prognostics

Abstract: Precursor parameters have been identified to enable development of a prognostic approach for insulated gate bipolar transistors (IGBT). The IGBT were subjected to thermal overstress tests using a transistor test board until device latch-up. The collector-emitter current, transistor case temperature, transient and steady state gate voltages, and transient and steady state collector-emitter voltages were monitored in-situ during the test. Pre- and post-aging characterization tests were performed on the IGBT. The aged parts were observed to have shifts in capacitance-voltage (C-V) measurements as a result of trapped charge in the gate oxide. The collector-emitter ON voltage VCE(ON) showed a reduction with aging. The reduction in the VCE(ON) was found to be correlated to die attach degradation, as observed by scanning acoustic microscopy (SAM) analysis. The collector-emitter voltage, and transistor turn-off time were observed to be precursor parameters to latch-up. The monitoring of these precursor parameters will enable the development of a prognostic methodology for IGBT failure. The prognostic methodology will involve trending precursor data, and using physics of failure models for prediction of the remaining useful life of these devices.

Physics-of-failure-based prognostics for electronic products:

Abstract: This paper presents a physics-of-failure (PoF)-based prognostics and health management approach for effective reliability prediction. PoF is an approach that utilizes knowledge of a product’s life cycle loading and failure mechanisms to perform reliability design and assessment. PoF-based prognostics permit the assessment of product reliability under its actual application conditions. It integrates sensor data with models that enable in situ assessment of the deviation or degradation of a product from an expected normal operating condition (ie, the product’s ‘health’) and the prediction of the future state of reliability. A formal implementation procedure, which includes failure modes, mechanisms, and effects analysis, data reduction and feature extraction from the life cycle loads, damage accumulation, and assessment of uncertainty, is presented. Then, applications of PoF-based prognostics are discussed.

Prognostics and Health Management of Electronics

Abstract: Reliability is the ability of a product or system to perform as intended (i.e., without failure and within specified performance limits) for a specified time, in its life-cycle environment. Commonly used electronics reliability prediction methods (e.g., Mil-HDBK-217, 217-PLUS, PRISM, Telcordia, FIDES) based on handbook methods have been shown to be misleading and provide erroneous life predictions. The use of stress and damage models permits a far superior accounting of the reliability and the physics of failure (PoF); however, sufficient knowledge of the actual operating and environmental application conditions of the product is still required. This article presents a PoF-based prognostics and health management approach for effective reliability prediction. PoF is an approach that utilizes knowledge of a product's life-cycle loading and failure mechanisms to perform reliability modeling, design, and assessment. This method permits the assessment of the reliability of a system under its actual application conditions. It integrates sensor data with models that enable in situ assessment of the deviation or degradation of a product from an expected normal operating condition and the prediction of the future state of reliability. This article presents a formal implementation procedure, which includes failure modes, mechanisms, and effects analysis, data reduction and feature extraction from the life-cycle loads, damage accumulation, and assessment of uncertainty. Applications of PoF-based prognostics and health management are also discussed. Keywords: reliability; prognostics; physics of failure; design-for-reliability; reliability prediction

A fusion prognostics method for remaining useful life prediction of electronic products

Abstract: Prognostics and health management methods can provide advance warning of failure; reduce the life cycle cost of a product by decreasing inspection costs, downtime, and inventory; and assist in the design and logistical support of fielded and future electronic products. Traditional prognostic methods, such as data-driven methods and physics of failure methods have some limitations. This paper presents a fusion prognostics method, which fuses data-driven methods and physics of failure methods to predict the remaining useful life of electronic products. This method integrates the advantage and overcome the limitations of the data-driven methods and the physics of failure methods to provide better predictions.

Encapsulation Technologies for Electronic Applications

Abstract: Electronics are used in a wide range of applications including computing, communication, biomedical, automotive, military and aerospace. They must operate in varying temperature and humidity environments including indoor controlled conditions and outdoor climate changes. Moisture, ionic contamination, heat, radiation and mechanical stresses are all highly detrimental to electronic devices and can lead to device failures. Therefore, it is essential that the electronic devices be packaged for protection from their intended environments, as well as to provide handling, assembly, electrical and thermal considerations.Currently, more than 99% of microelectronic devices are plastic encapsulated. Improvements in encapsulant materials, and cost incentives have stretched the application boundaries for plastic electronic packages. Many electronic applications that traditionally used hermetic packages such as military are now using commercial-off-the-shelf (COTS) plastic packages. Plastic encapsulation has the advantages of low cost, smaller form factors, and improved manufacturability. With recent trends in environmental awareness, new environmentally friendly or ' green' encapsulant materials (i.e. without brominated additives) have emerged. Plastic packages are also being considered for use in extreme high and low temperature electronics. 3-D packaging and wafer-level-packaging (WLP) require unique encapsulation techniques. Encapsulant materials are also being developed for micro-electro-mechanical systems (MEMS), bio-MEMS, bio-electronics, and organic light-emitting diodes (O-LEDs).This book offers a comprehensive discussion of encapsulants in electronic applications. The main emphasis is on the encapsulation of microelectronic devices; however, the encapsulation of connectors and transformers is also addressed. This book discusses 2-D and 3-D packaging and encapsulation, encapsulation materials including environmentally friendly 'green' encapsulants, and the properties and characterization of encapsulants. Furthermore, this book provides an extensive discussion on defects and failures related to encapsulation, how to analyze such defects and failures, and how to apply quality assurance and qualification process for encapsulated packages. This book also provides information on the trends and challenges of encapsulation and microelectronic packages including application of nanotechnology. . Guidance on the selection and use of encapsulants in the electronics industry, with a particular focus on microelectronics. Coverage of environmentally friendly 'green encapsulants'. Practical coverage of faults and defects: how to analyze them and how to avoid them

A Prognostics and Health Management Roadmap for Information and Electronics-Rich Systems

Abstract: Prognostics and systems health management (PHM) is an enabling discipline of technologies and methods with the potential of solving reliability problems that have been manifested due to complexities in design, manufacturing, environmental and operational use conditions, and maintenance. Over the past decade, research has been conducted in PHM of information and electronics-rich systems as a means to provide advance warnings of failure, enable forecasted maintenance, improve system qualification, extend system life, and diagnose intermittent failures that can lead to field failure returns exhibiting no-fault-found symptoms. This paper presents an assessment of the state of practice in prognostics and health management of information and electronics-rich systems. While there are two general methods of performing PHM, model-based and data–driven methods, these methods by themselves have some key disadvantages. This paper presents a fusion prognostics approach, which combines or “fuses together” the model-based and data–driven approaches, to enable markedly better prognosis of remaining useful life. A case study of a printed circuit card assembly is given in order to illustrate the implementation of the fusion approach to prognostics.

Model-based and data-driven prognosis of automotive and electronic systems

Abstract: Recent advances in sensor technology, remote communication and computational capabilities, and standardized hardware/software interfaces are creating a dramatic shift in the way the health of vehicles is monitored and managed. Concomitantly, there is an increased trend towards the forecasting of system degradation through a prognostic process to fulfill the needs of customers demanding high vehicle availability. Prognosis is viewed as an add-on capability to diagnosis that assesses the current health of a system and predicts its remaining life based on sensed features that capture the gradual degradation in the operation of the vehicle. This paper discusses a hybrid model-based, data-driven and knowledge-based integrated diagnosis and prognosis framework, and applies it to automotive (suspension and battery systems) and on-board electronic systems.

Early Detection of Interconnect Degradation by Continuous Monitoring of RF Impedance

Abstract: Traditional methods used to monitor interconnect reliability are based on measurement of dc resistance. DC resistance is well suited for characterizing electrical continuity, such as identifying an open circuit, but is not useful for detecting a partially degraded interconnect. Degradation of interconnects, such as cracking of solder joints due to fatigue or shock loading, usually initiates at an exterior surface and propagates toward the interior. At frequencies above several hundred megahertz, signal propagation is concentrated at the surface of interconnects, a phenomenon known as the skin effect. Due to the skin effect, RF impedance monitoring offers a more sensitive and reproducible means of sensing interconnect degradation than dc resistance. Since the operation of many types of electronic product requires transmission of signals with significant frequency components in the gigahertz range, this has the further implication that even a small crack at the surface of an interconnect may adversely affect the performance of current and future electronics. This paper demonstrates the value of RF impedance measurements as an early indicator of physical degradation of solder joints as compared to dc-resistance measurements. Mechanical fatigue tests have been conducted with an impedance-controlled circuit board on which a surface mount component was soldered. Simultaneous measurements were performed of dc resistance and time domain reflection coefficient as a measure of RF impedance while the solder joints were stressed. The RF impedance was observed to increase in response to the early stages of cracking of the solder joint while the dc resistance remained constant. Failure analysis revealed that the RF impedance increase resulted from a physical crack, which initiated at the surface of the solder joint and propagated only partway across the solder joint. A comparison between RF impedance and event detectors was made to compare their respective sensitivities in detecting interconnect degradation. These test results indicate that RF impedance can serve as a nondestructive early indicator of solder joint degradation and as an improved means for assessing reliability of high-speed electronics.

Warpage Analysis of Flip-Chip PBGA Packages Subject to Thermal Loading

Abstract: The aim of this paper was to measure and simulate the warpage of flip-chip PBGA packages subject to thermal loading (from room temperature to 260?C). In the experiments, a full-field shadow moirE? was used to measure real-time out-of-plane deformations (warpages) on the substrate and chip surfaces of the flip-chip packages under thermal heating and cooling conditions. A finite-element method (FEM) and Suhir's die-assembly theory, together with the measured material data (elastic moduli and coefficients of thermal expansion (CTEs) for organic substrates), were used to analyze the thermally induced deformations of the packages to gain insight into their mechanics. The strain gauge data used to determine the CTEs of the substrates also indicated that there was nearly no bending strain under thermal loading. The full-field warpages on the substrate surface of the packages from the shadow moirE? were documented under temperature loading. It was also found that there were different zero-warpage temperatures (which resulted in a variation of warpages at room temperature) for the four test packages during thermal loading, but they had similar warpage rates (the slope of warpage with respect to temperature). This might have been due to the creep of the underfill and the solder bumps in the packages at the solder reflow temperature. Regardless of the zero-warpage temperature, the warpage of the packages can be well simulated or predicted by FEM and Suhir's theory. The key material properties (elastic moduli and CTEs for the substrate and underfill) that affect the maximum warpage of the package were thoroughly studied. It was found that, among these material properties, a low elastic modulus for the underfill can significantly reduce the maximum warpage, while its CTE is much less sensitive to warpage. Moreover, the substrate CTE affects the warpage of a package only with noncompliant underfills, while a typical substrate elastic modulus (ranging from 10 to 30 GPa) is insensitive to warpage, unless its value is lower than a few gigapascals.

A Highly Accurate Method for Assessing Reliability of Redundant Arrays of Inexpensive Disks (RAID)

Abstract: The statistical bases for current models of RAID reliability are reviewed and a highly accurate alternative is provided and justified. This new model corrects statistical errors associated with the pervasive assumption that system (RAID group) times to failure follow a homogeneous Poisson process, and corrects errors associated with assuming the time-to-failure and time-to-restore distributions are exponentially distributed. Statistical justification for the new model uses theory for reliability of repairable systems. Four critical component distributions are developed from field data. These distributions are for times to catastrophic failure, reconstruction and restoration, read errors, and disk data scrubs. Model results have been verified and predict between 2 to 1,500 times as many double disk failures as estimates made using the mean time to data loss method. Model results are compared to system level field data for RAID group of 14 drives and show excellent correlation and greater accuracy than either MTTDL.

A hybrid prognostics and health management approach for condition-based maintenance

Abstract: Condition-based maintenance (CBM) is an efficient proactive maintenance strategy based on actual conditions obtained from in-situ, non-invasive tests, and operating measurement. In recent year, prognostics and health management (PHM) has emerged as one of the key enablers for achieving efficient system-level maintenance and for lowering life-cycle costs. This paper overviews methodology of physics-of-failure (PoF) approach and categorizes data-driven approach for the PHM application, summarizes their advantages and disadvantages respectively, and presents a hybrid prognostics approach which incorporate both the advantages of PoF and data-driven approaches for condition-based maintenance.

A Rapid Life-Prediction Approach for PBGA Solder Joints Under Combined Thermal Cycling and Vibration Loading Conditions

Abstract: While some electronic products are routinely subjected to concurrent vibration and temperature cycle loading, the ability to accurately model and estimate life expectancy of hardware under such conditions still presents a unique challenge. For combined vibration and temperature cycling, one of the most likely causes of failure is the fatigue of solder interconnects. This paper presents an approach to predict solder joint life under combined thermal cycling and vibration loading conditions, by taking into account temperature effects and loading interactions. Combined loading experiment on a test vehicle populated with PBGA packages was used to demonstrate this approach.

Critical Review of the Engelmaier Model for Solder Joint Creep Fatigue Reliability

Abstract: A solder interconnect fatigue life model was developed by Werner Engelmaier in the early 1980s as an improvement upon the inelastic strain range-based Coffin-Manson model. As developed, the model provides a first-order estimate of cycles to failure for SnPb solder interconnects under power and thermal cycles. While the model has been widely adopted for SnPb solder joint reliability prediction, many issues that arise from simplifications in formulating input model parameters as well as from the complex physics of solder degradation challenge the model's ability to accurately estimate cycles to failure. Deficiencies with the model have been reported by a number of researchers. This paper reviews and summarizes the major issues with the Engelmaier model in its applicability to predict solder joint thermal fatigue life.

An Assessment of Immersion Silver Surface Finish for Lead-Free Electronics

Abstract: The worldwide transition to lead-free electronics has increased the usage of several lead-free pad finishes for electronic assembly manufacturers, including immersion silver, immersion tin, electroless nickel-immersion gold, and organic solderability preservatives. This study assesses and compares immersion silver as a circuit board finish in terms of its ease of use, wettability, solderability, shelf life, appearance, solder joint strength, intermetallic and void formation, reliability, and costs.

Effects of Temperature Cycling and Elevated Temperature/Humidity on the Thermal Performance of Thermal Interface Materials

Abstract: Thermal interface materials (TIMs) have become increasingly important in reducing the interfacial thermal resistance between contacting surfaces inside electronic devices, such as at the die-heat-sink or heat-spreader-heat-sink interfaces. While the focus regarding implementing TIMs remains on reducing the thermal resistance path, the long-term performance of the TIM is important from a life-cycle standpoint. This paper presents test and analysis results examining the effect of temperature cycling and elevated temperature/humidity on the thermal performance of filled polymer TIMs using the laser flash method. A three-layer sandwich structure was used to simulate loading conditions encountered by TIMs in actual applications and to assess the change in their thermal resistances. The evaluated thermal resistance included contact and bulk resistances and was calculated using the Lee algorithm, an iterative method that uses the properties of the single layers and the three-layer sandwich structures. Test samples included three thermal putties, a gap filler, an adhesive, a gel, and two gap pads. For most materials, little change or slight improvement in the thermal performance was observed over the course of environmental exposures. Scanning acoustic microscope images revealed delamination in one group of gap pad samples and cracking in the putty samples as a result of temperature cycling. One thermal putty material showed degradation due to temperature cycling resulting from bulk material changes near the glass transition temperature, while other samples showed little change or slight improvement in the thermal performance over the course of temperature cycling.

Evaluation of pure tin plated copper alloy substrates for tin whiskers

Abstract: Purpose – The purpose of this paper is to present the results from work on a project aimed at evaluating six different copper alloy substrates coated with pure tin for tin whisker growth. The influence of intermetallic growth between the copper alloy substrate and the tin‐plating on the growth of tin whiskers has been investigated.Design/methodology/approach – The experiment consisted of six substrates of different alloys of copper, plated with bright tin including copper beryllium, cartridge brass, phosphor bronze, Cu‐Ni‐Si “7025” and Cu‐Ni‐Sn “spinodal”. The samples were mechanically stressed and then subjected to temperature humidity storage conditions for 1,000 h. These samples were then evaluated for tin whisker growth and intermetallic layer thickness.Findings – Of the six samples five showed tin whisker growth. For these samples the intermetallic layer thickness has little effect on tin whisker growth. Sample with Cu‐Ni‐Sn “spinodal” alloy substrate showed very low whisker density and comparatively...

Prognostics-based product qualification

Abstract: Qualification is the process of demonstrating that a product is capable of meeting or exceeding specified requirements. The specified requirements are expected to depend on the final product and its specific life cycle application conditions. In this paper, a prognostics-based qualification is proposed, which is more efficient and cost effective than the traditional qualification process. The approach does not require a product to fail in the test, because in addition to detecting failure, the health of the product is monitored, including degraded health and intermittent product disruptions. The results are a significant decrease in qualification time and much improved understanding of the product's reliability.

A fusion approach to IGBT power module prognostics

Abstract: In this paper, a framework for fusion approach to IGBT power module prognostics is reported. A failure modes, mechanisms, and effects analysis (FMMEA) for the IGBT power module is performed to identify critical failure mechanisms. For the failure mechanisms identified, relevant physics of failure models are discussed. In addition, the parameters affected by the critical failure mechanisms are identifed that are to be monitored in application. The implementation of this prognostics approach involves precursor parameter monitoring, parameter isolation and trending, and the use of relevant physics of failure models for remaining useful life estimates.

Health Monitoring and Prognostics of Electronics Subject to Vibration Load Conditions

Abstract: This paper discusses a health monitoring and prognostics methodology for assessing the reliability of a group of electronic components mounted on a printed circuit board by using strain gauges and an accelerometer to monitor the life-cycle vibration loads. These loads were converted into the component interconnects' stress values, which were then used in a vibration failure fatigue model for damage assessment. Damage estimates were accumulated using Miner's rule and then used to predict the life consumed and remaining life. The results were verified by experimentally measuring component lives through real-time daisy-chain resistance measurements.

Reliability design and case study of a refrigerator compressor subjected to repetitive loads

Abstract: A newly designed crankshaft of a compressor for a side-by-side (SBS) refrigerator was studied. Using mass and energy conservation balances, a variety of compressor loads typically found in a refrigeration cycle were analyzed. The laboratory failure modes and mechanisms were compressor locking and crankshaft wear. These were similar to those of the failed samples in the field. Failure analysis, accelerated life testing (ALT), and corrective actions were used to identify the key reliability parameters. The design parameters of the crankshaft included the hole locations and the groove of the crankshaft used for oil lubrication, crankshaft hardness, and thrust washer interference. Based on the analysis and design changes, the B 1 life of the new design is now over ten years with a yearly failure rate of 0.01 percent. A five step procedure is recommended for parts design.

Method to extract parameters from in-situ monitored signals for prognostices

Abstract: Through the methods of this invention, prognostics tools are provided to more efficiently and more accurately predict when a component product may fail. In a first embodiment a method is described whereby a number of environmental factors are monitored, the provided sensors obtaining raw data, variations in said raw data measured, the parameters of interest extracted and binned according to predetermined criteria, with the raw data thereafter discarded. In a second embodiment of the invention, the same sensor readings are recorded along with the performance characteristics for the component/product and compared to estimated performance for the product. The performance drift is then observed, whereby in monitoring said drift, trends may be determined and time or cycles to failure predicted.

Design of Experiments for Board-Level Solder Joint Reliability of PBGA Package Under Various Manufacturing and Multiple Environmental

Abstract: A design of experiments was conducted to determine the reliability of plastic ball grid array packages under various manufacturing and multiple environmental loading conditions. Parameters included conformal coating methods, underfill, solder mask defined, and non-solder mask defined pads. Board-level tem- perature cycling, vibration, and combined temperature cycling and vibration testing were performed to quantify the reliability and identify preferred design parameters. Through the main effects and interaction analysis, test results show underfill is the key parameter related to the solder joint reliability improvement. Conformal coat method and printed circuit board pad design are not main effects on solder joint reliability. No interactive relationship exists among these three factors under temperature cycling loading, but some interactive relationship between printed circuit board pad type and the conformal coating method exists under vibration and combined loading conditions. Index Terms—Conformal coating, design of experiment (DOE), non-solder mask defined (NSMD), plastic ball grid array (PBGA), solder mask defined (SMD), temperature cycling, underfill, vibration.

Design of Experiments for Board-Level Solder Joint Reliability of PBGA Package Under Various Manufacturing and Multiple Environmental Loading Conditions

Abstract: A design of experiments was conducted to determine the reliability of plastic ball grid array packages under various manufacturing and multiple environmental loading conditions. Parameters included conformal coating methods, underfill, solder mask defined, and non-solder mask defined pads. Board-level temperature cycling, vibration, and combined temperature cycling and vibration testing were performed to quantify the reliability and identify preferred design parameters. Through the main effects and interaction analysis, test results show underfill is the key parameter related to the solder joint reliability improvement. Conformal coat method and printed circuit board pad design are not main effects on solder joint reliability. No interactive relationship exists among these three factors under temperature cycling loading, but some interactive relationship between printed circuit board pad type and the conformal coating method exists under vibration and combined loading conditions.

Precursor parameter identification for power supply prognostics and health management

Abstract: Prognostics and health management (PHM) seeks to identify and isolate reliability problems in products (diagnostics) and predict a product's remaining useful life (prognostics). In this paper, a four-step PHM approach for power supplies is presented: 1) precursor parameter identification based on historical data analysis and failure mechanism analysis; 2) baseline establishment by conducting experiments under different environmental and usage conditions and characterizing precursor parameters for healthy power supplies; 3) baseline verification by conducting similar experiments for fielded power supplies; and 4) testing. Precursor parameter identification for one switch-mode power supply (SMPS) was carried out. The power metal-oxide semiconductor field-effect transistor, insulated-gate bipolar transistor, and the Schottky diode were identified as the majority cause by historical data analysis. Gate oxide leakage current, threshold voltage, transconductance, junction temperature, VCE (on), and contact resistance were determined to be monitored parameters for this SMPS after a failure mechanism analysis.

A framework for cost-effective and accurate maintenance combining CBM RCM and data fusion

Abstract: Cost-effectiveness and accuracy are two basic criteria for good maintenance. Reducing maintenance costs can increase net profit, while accurate maintenance actions can sustain continuous and reliable operation of equipment. As instruments and information systems tend to become cheaper and more reliable, condition-based maintenance has become an important tool for running a plant or a factory. This paper presents a novel condition-based maintenance framework that uses reliability-centered maintenance to save money and employs the data fusion strategy for improving condition monitoring, health assessment, and prognostics. This framework can help obtain optimal maintenance performance with good generality.

Effect of Lead-Free Soldering on Key Material Properties of FR-4 Printed Circuit Board Laminates

Abstract: The transition to lead-free soldering of printed circuit boards (PCBs) using solder alloys such as SnAgCu has resulted in higher temperature exposures during assembly compared with eutectic SnPb solders. The knowledge of PCB laminate material properties and their dependence on the material constituents, combined with their possible variations due to lead-free soldering temperature exposures, is an essential input in the laminate selection process. This paper provides laminate selection guidelines that were arrived at by assessing key material properties (glass transition temperature, coefficient of thermal expansion, decomposition temperature, and water absorption), and their responses to lead-free soldering assembly conditions. A range of commercially available FR-4 PCB laminate materials, classified on the basis of glass transition temperature (high, mid, and low), curing agents (dicyandiamide and phenolic), flame retardants (halogenated and halogen-free), and fillers (presence or absence) were studied. The laminate material properties under investigation were measured as per the IPC-TM-650 test methods before and after exposure to multiple lead-free soldering cycles. Combinatorial property analysis was conducted to investigate the causes behind variations in material properties.

Encapsulation Process Technology

Abstract: Encapsulation techniques used in electronic applications can be classified into five main technologies: molding, glob-topping, potting, underfilling, and printing. The selection of a suitable encapsulation method generally depends on several factors including equipment and labor cost, production volume, molding cycle, application requirements, package reliability, encapsulant material, and package type. Molding technologies used for the encapsulation of microelectronic devices include transfer molding, injection molding, reaction injection molding, and compression molding. Transfer molding is the most popular encapsulation method. Compression molding has application in multi-chip modules (MCM) packages and wafer-level packages (WLPs). Glob-topping is the direct encapsulation of the microelectronic device such as flip-chip and chip-on-board on the printed circuit board. It consists of two techniques: glob top and dam-and-fill. The potting method is generally used for the encapsulation of larger electronic units such as connectors and power supplies. Underfilling is used for encapsulating and protecting the solder-ball interconnects and flip-chip and BGA packages. The two most common encapsulation techniques used for 2D WLPs include compression molding and printing encapsulation. 3D packages are encapsulated in a variety of techniques. Conventional encapsulation methods such as transfer molding and injection molding can also be applied to stacked die packages with wire bonding.