Wire Bond Failure Research Articles

Real‐time reliability evaluation method for IGBT module in MMC based on junction temperature and bond wire failure online monitoring

AbstractThe lack of an MMC reliability evaluation approach that incorporates data on essential components' health monitoring in the already related research prevents reliability from being further improved. Therefore, this article proposes a real‐time reliability evaluation method of the multi‐state IGBT module in MMC through iterative calculation of the Markov chain model. The degradation process of the IGBT module is divided into multiple states based on the monitored bond wire failure, and the failure rate of the IGBT module is updated in real time using the accumulated monitoring data of junction temperature. The proposed method can more accurately reflect the real state of MMC compared with the binary state evaluation method. Besides, a multi‐channel high‐speed data acquisition board is designed to measuring the gate voltage and collector voltage of the IGBT for the health evaluation of IGBT modules in MMC; the typically measured results validate the effectiveness of the data acquisition board.

Bond Wire Fatigue of Au, Cu, and PCC in Power LED Packages.

Bond wire failure, primarily wire neck breakage, in power LED devices due to thermomechanical fatigue is one of the main reliability issues in power LED devices. Currently, the standard testing methods to evaluate the device's lifetime involve time-consuming thermal cycling or thermal shock tests. While numerical or simulation methods are used as convenient and quick alternatives, obtaining data from material lifetime models with accurate reliability and without experimental fatigue has proven challenging. To address this issue, a mechanical fatigue testing system was developed with the purpose of inducing mechanical stresses in the critical region of the bond wire connection above the ball bond. The aim was to accelerate fatigue cracks at this bottleneck, inducing a similar failure mode as observed during thermal tests. Experimental investigations were conducted on Au, Cu, and Pd-coated Cu bonding wires, each with a diameter of 25 µm, using both low- and high-frequency excitation. The lifetime of the wire bond obtained from these tests ranged from 100 to 1,000,000 cycles. This proposed testing method offers material lifetime data in a significantly shorter timeframe and requires minimal sample preparation. Additionally, finite element simulations were performed to quantify the stresses at the wire neck, facilitating comparisons to conventional testing methods, fatigue test results under various operating conditions, material models, and design evaluations of the fine wire bond reliability in LED and microelectronic packages.

Wire bond contact defect identification in battery modules of electric vehicles using pulses and differential voltage analysis

Automotive battery packs for electromobility applications consist of a large number of interconnected battery cells. Different cell-to-busbar joining techniques are utilized, with cylindrical cells frequently being contacted using wire bonding. Failure of individual connections can occur due to strong vibrations during operation and improper stress, making detection by the battery management system a necessity. This study investigates the identification of an electrical wire bond failure in a state-of-the-art electric vehicle module of a Lucid Air with 10 series-connected and 30 parallel-connected cells (10s30p). Four individual cells were characterized extensively in order to generate a simulation model taking into account parameter scatter. The failure case under investigation was simulatively incorporated in one parallel circuit and subsequently replicated in experimental validation measurements at the module level. The results show that this defect can be detected using pulses of C/3 or higher currents at various states of charge. An even more robust detection is achieved using differential voltage analysis of constant current C/20 discharge voltage trajectories. This defect identification method does not require any additional measurement sensors beyond the voltage taps and sensors provided by the manufacturer – with one voltage sensor per parallel circuit – and can therefore be implemented during electric vehicle usage, e.g. at dedicated service checks. A discussion on the applicability and scalability as well as the limitations of the method is provided. All measurement data of the state-of-the-art Lucid battery system is available as open source alongside the article.

Difference Between the PWM and Standard DC Power Cycling Tests Based on the Finite-Element Simulation

PWM power cycling, which has complex control strategies and high testing costs, received a lot of attention in recent years due to the test conditions are closer to the application of power modules than standard DC power cycling. Therefore, the root difference of the failure modes and lifetime of IGBT power modules between DC and PWM power cycling is the concern in this paper, based on the finite element simulation. For stimulating the PWM power cycling with high accuracy and fast speed, an IPWM power cycling is proposed and verified by a simple model. Then an electro-thermo-mechanical coupled model of a single chip is established for comparison. Mainly focus on the current distribution, temperature distribution and stress distribution. The current distribution comparison results show no difference while a higher temperature gradient is shown in PWM power cycling due to the additional switching losses. However, the stress distribution results show chip solder layer is still the main failure mechanism both in DC and IPWM power cycling. Therefore, a conclusion can be obtained that there is no difference in failure mechanism and lifetime between DC and PWM power cycling. And the same bond wire failure and similar lifetime of DC and PWM power cycling tests further verify this conclusion.

Load Current Injection Modes Affected Power Cycling Lifetime and Failure Mechanism of IGBTs

In this paper, the influence of load current injection modes (saturation mode and threshold mode), at standard DC power cycling, on the failure mechanism and lifetime of IGBTs is presented. 6 groups of power cycling tests, at almost the same test conditions, with 2 different current injection modes and 2 different packages are performed. The failure mode after power cycling is confirmed by on-line monitored electrical and thermal parameters (forward voltage drop <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">CE</sub> and thermal resistance <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">thjs</sub> ) and further by SAM (Scanning Acoustic Micrography) pictures. Failure mechanism is then analyzed and the power cycling lifetime is compared and explained, with the help of finite element simulations. All results show that the threshold load current injection mode, with the gate and collector shorted, in power cycling can indeed reduce the load current to a large extent for the desired junction temperature swing. However, the power cycling lifetime and failure mechanism are changed, especially for devices with bond wire failure. It is not recommended for power cycling lifetime evaluation.

Investigation of CuAl IMCs Corrosion in Chloride Environment and its Prevention Strategy

Abstract In most current wire-bonding applications, electrical interconnection is accomplished by fine Cu wires bonded to Al bonding pads microfabricated on an IC chip and external contact pins of the PCB board. Corrosion-related failure defects between the Cu wire and Al bond pad have been an ongoing un-trackable reliability issue plaguing the IC packaging industry for the past ten years, despite approaching ppb levels. Most prior studies hypothesized that intermetallic compounds (IMCs) like Cu9Al4, and CuAl2 were responsible for the observed acute wire-bond lift-off corrosion defects. Further studies sought to quantify the rates of corrosion of these IMCs and explore the effects of mitigation efforts of adding Pd, relevant to Pd-coated Cu wire-bonding. However, utilizing a novel real-time corrosion screening approach, we previously established that peripheral bimetallic contact between Cu ball-bonds and Al bond pads also plays a substantial role in the aggressive Al pad corrosion, induced by chloride ion penetration, which often leads to device failure. In this work, we further explored the role of IMCs corrosion in wire-bond lift-off failure utilizing fundamental electrochemical studies to quantify rates of galvanic-induced corrosion of IMCs within the broader context of an interconnected stack of Al bond pad, Cu-Al IMCs and Cu bonding wire. We also explored the use of a corrosion inhibitor to suppress the galvanic corrosion currents of Al bond pad, and Al-rich IMCs when electrically connected to Cu wire or Cu-rich IMCs.

In Situ Diagnosis of Multichip IGBT Module Wire Bonding Faults Based on Collector Voltage Undershoot

Condition monitoring of insulated gate bipolar transistor (IGBT) modules is an effective way to improve the transient performance and reliability of modular multilevel converters (MMC). This article proposes a novel bond wire failure monitoring method for the multichip IGBT modules in the MMC half-bridge submodule (SM) structure. The collector voltage undershoot <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">CA(np)</sub> of the complementary IGBT switch is measured during the turn- <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> switching transition of the controlled IGBT switch. <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">CA(np)</sub> is sensitive to the induced voltage over the stray inductance of the IGBT bond wires and provides high sensitivity as a health indicator. The non-intrusive measurement technique is demonstrated using a half-bridge circuit during the turn- <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> transition of the controlled IGBT, while its complementary switch (i.e., the device under test) is in the <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> state. Theoretical analysis and experimental results show that the parametric drift due to wire bonding failures can be effectively monitored with high specific relative sensitivity and granularity. To ensure its effectiveness in practical applications, the influence of load current, SM capacitor voltage, and junction temperature is discussed. In addition, a readout circuit is designed featuring the integrated desaturation detection and voltage peak detection, which offers both the short-term overcurrent fault protection and long-term bond wire aging monitoring functions.

Online correction method of IGBT lifetime evaluation based on bonding wire failure monitoring

Insulated gate bipolar transistor (IGBT) modules are widely used as power switching devices. In actual working conditions, the failure of bonding wires is one of the most important failure modes. At present, the influence of bonding wire failure is not considered in the reliability evaluation of the device, resulting in a large error in the life prediction result. Therefore, this paper proposes a life evaluation method for IGBT modules that takes into account the failure of the bonding wire. The transient thermal impedance of 1200 V/50 A IGBT module under the failure conditions of different numbers of bonding wires is calculated by constructing a finite element simulation model of device electro-thermal coupling. Both simulation and experimental results show that with the increase of the number of bonding wire failures, the transient thermal impedance curve of the device rises and the steady-state thermal impedance increases. The Foster thermal network models of the devices are updated, and the number of power cycles of the device with bonding wire failure under DC and sinusoidal pulse width modulation (SPWM) conditions is calculated. When the number of bonding wire failures and fatigue accumulation have a linear relationship, the life will be reduced by 48.29% compared to the healthy state.

Analysis of the IGBT Module with Bonding Wire Failure Based on Transient Thermal Impedance

Insulated gate bipolar transistor(IGBT) modules are widely used in inverters as power switching devices. In actual working conditions, the failure of bonding wires is one of the most common failure modes. In the current device reliability evaluation, the influence of bonding wire failure is ignored, which may easily cause the subsequent evaluation results to deviate from the reality. In this paper, the influence of the gradual failure of the bonding wire on the transient thermal impedance of the device is explored, and the electro-thermal coupling model of the device is constructed. The simulation results show that the transient thermal impedance of the device increases with the gradual failure of the bonding wire. An experimental platform for transient thermal resistance measurement was built to verify the accuracy of the simulation results.

Research on the Influence of Bond Wire Lift-Off Position on the Electro-Thermal Characteristics of IGBT

Based on the actual packaging structure of insulated gate bipolar transistor (IGBT) module, this article establishes the power loss model, and analyzes the influence of the position of the lift-off bond wire on the module. Through the theoretical analysis, it is found that the position of the lift-off bond wire is an important factor affecting the aging of the modules. And then the electrothermal coupling model of IGBT is established for simulation, and an experimental platform is built for verification. The results show that the distribution of bond wire lift-off position is one of the characteristics of bond wire failure. When the bond wire lift-off failure is concentrated on a single IGBT chip, it will accelerate the aging process of the modules. Therefore, this article considers that the position of the lift-off bond wire is a significant factor in the aging process of the modules, which should be fully considered in the bond wire state evaluation. In addition, the research results of this article can also provide theoretical reference for the optimization of IGBT module packaging structure.

The Impact of Gold Plating Process for Bonding Pads on Interconnection Quality

Ball-wedge bonding wires are widely used in microwave circuits and chip packaging. Plating process is an important factor that affects the interconnection quality of ball-wedge bonding wires. In this article, the impact of Gold (Au) plating processes for bonding pads on interconnection quality was studied using model analysis and experimental testing. For this purpose, printed circuit boards (PCBs) were manufactured using both electroless Nickel immersion Gold (ENIG) process and electroplating soft Gold process. The thickness and roughness of Gold plating layer of circuit boards were measured. For circuit boards with different Gold plating processes, based on the material and size parameters of ball-wedge bonding wires and pads, a finite element analysis (FEA) model of connection area was developed. the deformations and von-Mises stresses at the interfaces between bonding points and Gold-plated layers under tensile force were calculated and analyzed. The maximum tensile breaking force and qualified rate of ball-wedge bonding wires were analyzed from the perspectives of both thickness and roughness of Gold plating layer. In addition, the bonding wire failure modes were also observed and analyzed. The results of this investigation provide the theoretical support for selection of Gold plating processes in Gold wire bonding.

Multi-Chip IGBT Module Failure Monitoring Based on Module Transconductance with Temperature Calibration

The Insulated Gate Bipolar Transistor (IGBT) is the component with the highest failure rate in power converters, and its reliability is a critical issue in power electronics. IGBT module failure is largely caused by solder layer fatigue or bond wires fall-off. This paper proposes a multi-chip IGBT module failure monitoring method based on the module transconductance, which can accurately monitor IGBT module chip failures and bond wire failures. The paper first introduces the failure mechanism and module structure of the multi-chip IGBT module; then, it proposes a reliability model based on the module transconductance and analyzes the relationship between chip failure, bond wire failure, and the transmission characteristic curve of the IGBT module. Finally, the module transconductance under chip failure and bond wire failure is measured and calculated through simulation, and the temperature is calibrated, which can eliminate the influence of temperature on health monitoring. The results show that the method has a high sensitivity to chip failures and bond wire failures, can realize the failure monitoring of multi-chip IGBT modules, and is of great significance for improving the reliability of power converters.

The Impact of Connection Failure of Bonding Wire on Signal Transmission in Radio Frequency Circuits

Bonding wires are widely used in microwave circuits and chip packaging. The exposure to harsh environments may lead to connection failure in these wires. In this article, the impact of such failures on signal transmission was studied using model analysis and experimental testing. The effects of gold bonding wire failure on both the dc and high frequency characteristics were analyzed. Signal reflection and loss caused by failed gold bonding wire at different positions and a number of failed gold bonding wire were also investigated. Based on computational electromagnetics and transmission line theory, a 3-D electromagnetic field numerical calculation model and a distributed parameter circuit model were developed. The electromagnetic field model results are in good agreements with those obtained from the distributed parameter circuit model. The results obtained by the model simulation are validated using experimental tests. The results of this investigation provide a better understanding of the influence of the position and the number of failed bonding wires on the signal integrity of the circuit and theoretical support for identifying failure features in fault diagnosis.

A Health Monitoring Method for Bond Wires in IGBT Modules Based on Voltage Ringing Characteristics

Bond wire failure is a common failure that seriously affects the reliability of insulated-gate bipolar transistor (IGBT) modules. Real-time health monitoring for bond wires is very important to avoid catastrophic failures. In this article, we introduce a new health monitoring method for bond wires in IGBT modules based on the voltage ringing characteristics. We applied a double pulse circuit to generate voltage ringing in IGBTs and freewheeling diodes (FWDs) during turn off and reverse recovery phases. To monitor bond wire failure, we theoretically and experimentally validated the overshoot and oscillation frequency as indicators. In particular, we investigated the effects of the junction temperature and operating conditions on the overshoot and proposed their influence functions. We designed a measurement circuit to identify small changes in the overshoot. Finally, the health baselines for the overshoot under different conditions were experimentally verified. The novelty of the research lies in the accurate online monitoring for bond wire failure in IGBT modules without any external injection; the measurement circuit adopts the interrupt mode to save the controller resources. Our experimental results showed that after half the bond wire of the IGBT and the FWD failed, their voltage overshoot increased by nearly 5%.

Life prediction of copper wire bonds in commercial devices using principal component analysis (PCA)

Copper has been widely adopted as a viable alternative to gold for wire bonding, due to its lower cost, better electrical and thermal conductivity, lower tendency for wire sweep due to a higher modulus and slower intermetallic compound (IMC) formation with aluminum bond-pad. However, these IMCs can cause an increase in resistance and separation between bonding interface which causes an open circuit. Wire bond and component reliability must consider all factors in combination with the change of wire bond materials and processes. How can users of off-the-shelf components determine the effects of wire bond material changes on the reliability of the components in their systems? How will these changes affect high reliability applications such as automotive, military and harsh environments?Although physics-of-failure based models can represent the failure mechanisms individually, the complex nature of the mixed failure mechanism has inhibited development of an analytical equation to represent it. In addition, geometrical and material characteristics of the entire package along with bonding process parameters play a crucial role in magnitude of stress experienced by these bonds, portraying difficulty in developing one such equation for use to all copper wire bonded devices. This study has aimed to develop a data-based predictive method based on the principal component analysis technique to provide an estimate of the wire bond time to failure for plastic encapsulate components. Extensive thermal cycling experiments have been performed on multiple commercial devices to obtain training data for the model. This method of wire bond fatigue and failure prediction is an adaptive technique which can achieve greater accuracy as more data is added. This method aims to provide a life-time estimate of copper wire bonded component with inputs such as initial geometrical, material properties, and wire bond related attributes for a specific package.

A Method to Monitor IGBT Module Bond Wire Failure Using On-State Voltage Separation Strategy

On-state voltage is an important thermal parameter for insulated gate bipolar transistor (IGBT) modules. It is employed widely to predict failure in IGBT module bond wires. However, due to restrictions in work environments and measurement methods, it is difficult to ensure the measurement accuracy for the on-state voltage under practical working conditions. To address this problem, an on-state voltage separation strategy is proposed for the IGBT modules with respect to the influence of collector current (Ic) and junction temperature (Tj). This method involves the separation of the on-state voltage into a dependent part and two independent parts during the IGBT module bond wire prediction. Based on the proposed separation strategy, the independent parts in the failure prediction can be removed, making it possible to directly monitor the voltage variations caused by bond wire failure. The experimental results demonstrate that the proposed diagnosis strategy can accurately predict the bond wire failure stage in an IGBT module under different conditions.

Comparative Study of Chloride and Fluoride Induced Al Pad Corrosion in Wire Bonded Packaging Assembly

Microelectronics are used in virtually all electronic equipment’s nowadays ranging from medical instruments, automobiles, computers, cell phones and home appliances. Wirebonding process which connects the chip to the lead frame in IC packaging plays a very important role in the commercial production of IC’s. Chip usually consists of Al bond pads with Cu/Au wires. Thin film Al bond pads are easily vulnerable to corrosion in presence of contaminants and moisture. Bond pad corrosion is one of the common modes of corrosion failure in wire-bonded devices IC packaging. Improper rinsing, packaging and passivation defects allows moisture and contaminants into bondpads resulting in severe corrosion. Most common source of this corrosion comes from the presence of halide ions contamination as (Cl-, F-, Br- etc.) However, the corrosion morphology and the severity varies from different ions contamination as the chemistry governing the corrosion differs from one ion to another. Our research is focused on key findings on corrosion of Aluminum bond pad due to chloride (Cl-) and fluoride (F-) contamination. Our central motivation is to identify this F- corrosion mechanism, so that it will help to develop a strategy to prevent it and study the comparison between Cl- and F- Corrosion using Micro-pattern corrosion screening technique, Wire-bonded device (WBD) and other characterization technique such as GC-MS, SEM and tafel. GC-MS reveals that H2 gas evolution is observed during Cl- corrosion of the WBD, whereas little or no H2 evolution is observed during F- corrosion. SEM and EDX reveals no presence of Cl- in the corroded areas of its corrosion, whereas strong F- signal is observed in F- corrosion of the bondpads revealing, that the corrosion products formed on the surface has very poor solubility showing that Cl- and F- has a complete different corrosion morphology. Striking contrasts in corrosion morphology observed during the Cl- and F- corrosion were explained in the present work and will lead to better understanding of factors influencing the bond pad corrosion leading to the wire bond failure in IC packaging devices. [Fig. 1] Figure 1

Understanding Non-Stick on Lead Wirebond Failure Due to Leadfinger Surface Roughness

Understanding Non-Stick on Lead Wirebond Failure Due to Leadfinger Surface Roughness

Reliability model of bond wire fatigue for IGBT in MMC with system redundancy consideration

Reliability is a significant factor in the operation of the modular multilevel converter (MMC). Since the bond wire fatigue is one of the dominant failures of the insulated-gate bipolar transistor (IGBT) in the aging aspect, the wire bond lifetime related research has captured much attention in recent years. However, at system level, the redundancy of the system is seldom discussed in the reliability analysis of MMC. This paper proposes a reliability model for wire bond failure of IGBT with system redundancy consideration. The reliability model for IGBT at the component level is established based on the lifetime model. Also, the reliability model for the system with redundancy is built by the end-of-life cumulative distribution obtained from Monte Carlo method. The unreliability change of system level and component level are compared, and the influence of bridge arm redundancy on system reliability is also analyzed.

Diagnostics and Prognostics of Wire-Bonded Power Semi-Conductor Modules subject to DC Power Cycling with Physically-Inspired Models and Particle Filter

This paper presents an algorithm for determining the State of Health (SoH) and the Remaining Useful Life (RUL) of wire-bonded power semi-conductor modules. It is hybrid in the sense that it combines the estimations of physically-inspired models and the on-line data acquisition. A key aspect is the analysis, modeling, estimation, correction and exploitation of the on-state voltage Von evolution. In this paper, the algorithm is demonstrated with a particle filter and with power cycling experimental tests performed until complete wire-bond failure.