Wire Bond Research Articles

Online Recognition of Fallen-Off Bond Wires in IGBT Modules.

As a core component of power conversion systems, insulated gate bipolar transistor (IGBT) modules continually suffer from severe thermal damage caused by temperature swings and shear stress, resulting in fatigue failure. Bond wires falling off is one of the failure modes of IGBT modules. Given that the number of fallen-off bond wires is a significant parameter to evaluate the health status of the IGBT modules, this paper proposes an online identification model to recognize the number of fallen-off bond wires during normal operation. Firstly, a database containing datum Vce,on-Tj-IC (collector-emitter on-state voltage Vce,on, chip junction temperature Tj, collector current IC) planes with different fallen-off bond wires is built based on an offline aging test. Secondly, a Foster network model and a special circuit are designed to measure the junction temperature Tj and the collector-emitter on-state voltage Vce,on, respectively. Thirdly, the feature points of the IGBT module represented by Vce,on, Tj, and IC are given to the database to recognize the number of fallen-off bond wires according to the position of the feature points in the datum plane. The experimental results show that the proposed method can determine the fallen-off bond wires under the operation condition.

Modern Trends in Microelectronics Packaging Reliability Testing.

In this review, recent trends in microelectronics packaging reliability are summarized. We review the technology from early packaging concepts, including wire bond and BGA, to advanced techniques used in HI schemes such as 3D stacking, interposers, fan-out packaging, and more recently developed silicon interconnect fabric integration. This review includes approaches for both design modification studies and packaged device validation. Methods are explored for compatibility in new complex packaging assemblies. Suggestions are proposed for optimizations of the testing practices to account for the challenges anticipated in upcoming HI packaging schemes.

Computational multiscale modelling of material interfaces in electrical conductors

Material interfaces occur at various length scales and may exhibit significantly different properties than the surrounding bulk. Motivated by their importance for electrical engineering applications such as wire bonds and electrically conductive adhesives, the focus of the present work is on material interfaces in electrical conductors. In order to approximate the physical interphase (of finite thickness) as a (zero-thickness) cohesive zone-type interface in macroscale simulations, scale-bridging relations are established that relate the apparent electro-mechanical interface properties to the underlying microstructure. A finite element-based implementation is discussed with particular focus lying on the efficient calculation of the flux-type macroscale quantities and the associated generalised algorithmic consistent tangent stiffness tensors. Analytical solutions are derived for validation purposes and representative boundary value problems are studied.

Coupled thermal-mechanical analysis of power electronic modules with finite element method and parametric model order reduction

This work presents a new approach for performing a parametric study and examining nonlinear material behaviours of a coupled thermal-mechanical model of a Power Electronics Module (PEM) by integrating the Finite Element Method (ANSYS-FEM) with Parametric Model Order Reduction (pMOR). The considered coupling method solves the thermal and structural models concurrently compared to the widely practised sequential coupling method. Instead of constant parameter values, which are generally regarded for pMOR studies, the temperature-dependent material properties of the wire material have been parametrised in the work using the pMOR method. A generalised 2D model has been regarded here for thermal-mechanical analysis with the pMOR approach, parametrising temperature-dependent coefficient of thermal expansion (CTE) and Young’s modulus (E) of the wire material to explore their impact on wire bonds. The matrix interpolation method has been applied here for the pMOR study, and PRIMA, a Krylov subspace-based model order reduction (MOR) technique, has been exercised for local model order reductions. A new efficient process of matrix interpolation, based on the Lagrange interpolation technique, has been developed to implement matrix interpolation in the parametric reduced order model (pROM). The local reduced order models (ROMs) have a degree of freedom (DOF) of just 8, compared to the full-order models’ (FOMs) of 50,602. The pROM provides an excellent solution and reduces computational time by 84% for the presented case.

Silver Bonding Wire - an Alternative for Mechanical Sensitive Chip Configurations in Automotive Electronics Packaging

Silver (Ag) bond wires are mainly used in consumer products as a reliable low-cost alternative to gold (Au) bond wires. In previous investigations, we have shown that silver wires also have potential for use in the automotive sector (1, 2, 3, 4], where the materials are exposed to particularly harsh environmental conditions. In order to understand thc intluence of these conditions in the electronic package on the silver-aluminum material system, we carried out extensive studies on test packages built on laboratory level. For the future development of challenging automotive devices, it will be important to have a cooperation between semiconductor package developer and material supplier with an assist of characterization spccialists. In this project, we formed a threeparty project in which characterization specialists, package developer, and wire manufacturer collectivcly conduct a feasibility study of a new Ag wire material for automotive application. Two wire types (standard Ag wire and new type of Ag wire GX2s) were chosen for the investigation in direct comparison regarding long-term reliability. Samples were built under mass production conditions and then subjected to various reliability tests following AEC-Q006 requirements. Subsequently, mechanical characterizations by means of ball shear and pull tests as weil as high resolution SEM microstructure analyses on cross-section samples are applied. In the paper, results of the different tests will be summarized, but a more in-depth analysis will be given to the temperature cycle test (TCT), where the most significant differences between the sample variations occurred. Overall, the results show the importance of the knowledge for the material reliability upfront a device qualification process (robustness validation) and give further guidance for material selection.

A comprehensive packaging solution from DC to 113 GHz for InGaAs amplifiers

AbstractThis letter presents the design, fabrication and measurement of a 72 kHz to 113 GHz ultra‐broadband amplifier that includes a direct current (DC)‐blocking functionality. This amplifier module stands out with a high average gain of 12.5 dB in the frequency range from almost DC to 110 GHz. This work not only combines electrical interconnections but also mechanical design considerations, thermal requirements and practical application specific aspects. To ensure a low thermal resistance, the InGaAs amplifier IC is directly mounted on an aluminium submount, applying an advanced gluing concept, and interconnected to an input and output 50 grounded coplanar waveguide by wire bonds with a length of only 135 . To enable convenient usage of the package, 1 mm connectors are utilized. This amplifier module exhibits excellent thermal behaviour and group delay characteristics, making it an ideal choice for use in optical data transmission experiments.

A Bond Wire Aging Monitoring Method for IGBT Modules Based on Back Propagation Neural Networks

A Bond Wire Aging Monitoring Method for IGBT Modules Based on Back Propagation Neural Networks

Exploration of Interfacial Materials Chemistry Control to Improve Cu Wire Bonding Reliability

Copper wire bonding, with its advantages of higher electrical conductivity and better mechanical strength, has replaced gold wire bonding as a proven cost-effective electrical interconnection solution for IC packaging for the past 15 years. Early development of Cu wire bonding required overcoming of several technical challenges including bond pad damage caused by copper’s hardness and brittleness relative to gold. A more chemistry related challenge of using Cu as bonding wire is its well-known reactivity with oxygen. Inert atmospheric envelope of forming gas surrounding bonding capillary was developed to prevent oxidation of Cu wire during electronic flame off to enable a strong bonding. Another more elusive materials-chemistry related reliability challenge, with a typical low ppm occurrence, has been the chloride-induced corrosion defects between the Cu wire and Al bond pad. The opportunistic low-level chloride contaminations can originate from various points of packaging manufacturing process flow and often render it un-trackable. In this talk, we present recent efforts to systematically control interfacial materials chemistry across Cu bonding wire, Cu/Al bimetallic contacts and CuxAly intermetallic compounds with the aim to eliminate corrosion defects and improve the overall bonding reliability. The current prevailing manufacturing solution is to utilize Pd-coated Cu bonding wire that can only partially mitigate the CuxAly intermetallic corrosion vulnerability. We utilized a real-time corrosion screening metrology to explore the underlying interfacial materials chemistry drives vigorous corrosion between Cu wire and Al bond pad when exposed to trace level of chloride contaminant. Combining with SEM, sensitive infrared spectroscopy and electrochemical characterization, our data show strategic surface modification on both Cu bonding wire and exposed CuxAly intermetallic can have a significant impact on reducing corrosion defect rates. The obtained mechanistic insights provide several new strategies enabled by a novel Cu-selective passivation coating technology to effectively mitigate Cu wire bonding corrosion defects. Implications on further improving overall Cu wire bonding reliability will be present based on these new approaches that have low-cost and packaging friendly advantages.

Al2O3-Coated Bonding Wire with Electrical Insulation & Promoted Adhesion

Conventional bond wires composed of Au, Ag, & Cu don’t meet market demands for strong adhesion, electrical insulation, and corrosion passivation due to their conductive metallic surfaces. We propose a solution through the applications of a ceramic (Al2O3) coating at nanometer scales on these metal wires, thereby improving their adhesion to encapsulation, electrical insulation, and resistance to corrosion. We used ALD (Atomic Layer Deposition) methods to coat Au and Ag metal wires with diameters ranging from 18um to 48um (0.7mil~1.9mil) with Al2O3. Our paper details the innovative processes we used to incubate the idea of Al2O3 coating on conventional bond wires, focusing on wire bondability and dependability. Our findings demonstrate enhanced electrical insulation between crossing wires and increased reliability related to the wires’ adhesion to encapsulation.

Gold Coated Silver Bonding Wire and Its Consistent Reliability Performances

Thermal aging of gold coated silver bonded ball with aluminium bond pads exhibited a stable interface without Kirkendall voids until 4000h at 200°C for an un-molded device tested under vacuum. Ball and stitch pull remains in strength and remained constant until 4000 hours of aging. The growth of aluminides at the bond interface is about 4.5µm for 4000 hours of aging. The electrical resistance of the bonded ball remains the same until 4000 hours at 175°C for an epoxy molded device, molded with 5 to 7 pH green epoxy molding compound containing low chlorine and sulfur. Interestingly, the bonded ball interface of epoxy molded device has sustained 480h on biased Highly Accelerated Stress Test (bHAST) at +20V bias, 130°C, 85%RH. The bonded ball interface is stable until 1000 hours on unbiased HAST (uHAST) at 130°C, 85% RH as well. Cross-sectional ovservations of the bonded balls revealed the presence of intermetallic phases at the bond interface. However, formation of Kirkendall voids or crack propagatioon due to galvanic corrosions are absent.

Thermal Misfit and Diffusion Induced Stresses of Cu-Al Intermetallics in Microelectronics Wire Bonding

The thermosonic bonding technique is a widely used method for Cu wire interconnections. However, issues arise due to volumetric changes in intermetallic compounds (IMCs) formed at the Cu-Al bonding interface, leading to voids in the Cu-Al IMC layer. This problem is exacerbated after annealing, such as in high-temperature Storage (HTS). In this study, a statistical modelling approach was employed to quantitatively analyse stress, studying the evolution and characteristics of the interfacial microstructure in the thermosonic Cu wire-Al bond pad system. Microstructural analysis focused on Cu-Al IMC crystallography and compositional classification. A stress model was proposed, considering both thermal misfit and diffusion-induced stresses. Results showed that interfacial stress generally increased with higher bonding temperatures. The influence of forming gas supply was relatively minor, with oxide layers minimally impeding Cu-Al interdiffusion during Cu-Al IMC formation. This stress modelling technique hold potential as a valuable failure analysis tool for implementing Cu wire in various industries.

First experimental evaluation of a high-resolution deep silicon photon-counting sensor.

Current photon-counting computed tomography detectors are limited to a pixel size of around 0.3 to 0.5mm due to excessive charge sharing degrading the dose efficiency and energy resolution as the pixels become smaller. In this work, we present measurements of a prototype photon-counting detector that leverages the charge sharing to reach a theoretical sub-pixel resolution in the order of . The goal of the study is to validate our Monte-Carlo simulation using measurements, enabling further development. We measure the channel response at the MAX IV Lab, in the DanMAX beamline, with a 35keV photon beam, and compare the measurements with a 2D Monte Carlo simulation combined with a charge transport model. Only a few channels on the prototype are connected to keep the number of wire bonds low. The measurements agree generally well with the simulations with the beam close to the electrodes but diverge as the beam is moved further away. The induced charge cloud signals also seem to increase linearly as the beam is moved away from the electrodes. The agreement between measurements and simulations indicates that the Monte-Carlo simulation can accurately model the channel response of the detector with the photon interactions close to the electrodes, which indicates that the unconnected electrodes introduce unwanted effects that need to be further explored. With the same Monte-Carlo simulation previously indicating a resolution of around with similar geometry, the results are promising that an ultra-high resolution detector is not far in the future.

A Bond Wire Aging Monitoring Method for IGBT Modules Based on Bond Wire Degradation Voltage

A Bond Wire Aging Monitoring Method for IGBT Modules Based on Bond Wire Degradation Voltage

Investigation of laser wire bonding for the fabrication of tensegrity structures

Tensegrity structures are structures in which elements stabilize each other by bearing compressive or tensile loads. They have a high potential for lightweight design. As structures with tensile loads, wires can be used that are connected to other structures using a laser bonding process. Investigations of bonding a mild steel wire with a diameter of 1 mm onto a flat substrate have been conducted using a coaxial deposition welding head. The influence of the parameters focus position, laser power, wire feed rate and bonding processing time has been investigated regarding the bonding quality. A process window for a stable process and a sufficient bond of wire and substrate was determined. The laser intensity and stickout length have a significant influence on the bonding. High intensities and stickout lengths lead to wire burn back and no bond with the substrate while wire backup occurred at low intensities and stickout lengths.

Cryogenic characterization of Hamamatsu HWB MPPCs for the DUNE photon detection system

The Deep Underground Neutrino Experiment (DUNE) is a next generation experiment aimed to study neutrino oscillation. Its long-baseline configuration will exploit a Near Detector (ND) and a Far Detector (FD) located at a distance of ∼1300 km. The FD will consist of four Liquid Argon Time Projection Chamber (LAr TPC) modules. A Photon Detection System (PDS) will be used to detect the scintillation light produced inside the detector after neutrino interactions. The PDS will be based on light collectors coupled to Silicon Photomultipliers (SiPMs). Different photosensor technologies have been proposed and produced in order to identify the best samples to fullfill the experiment requirements. In this paper, we present the procedure and results of a validation campaign for the Hole Wire Bonding (HWB) MPPCs samples produced by Hamamatsu Photonics K.K. (HPK) for the DUNE experiment, referring to them as `SiPMs'. The protocol for a characterization at cryogenic temperature (77 K) is reported. We present the down-selection criteria and the results obtained during the selection campaign undertaken, along with a study of the main sources of noise of the SiPMs including the investigation of a newly observed phenomenon in this field.

Estimating of IGBT Bond Wire Lift-Off Trend Using Convolutional Neural Network (CNN)

Estimating of IGBT Bond Wire Lift-Off Trend Using Convolutional Neural Network (CNN)

Failure Mechanism Investigations of Bond Wires Lifting-Off and Die-Attach Solder Aging Considering the Thermal Coupling Effects

Failure Mechanism Investigations of Bond Wires Lifting-Off and Die-Attach Solder Aging Considering the Thermal Coupling Effects

Optimization of Wire-bonding Process Parameters for Gold Wire and Aluminium Substrate using Response Surface Method

Wire bonding is a connecting technique that uses a combination of temperature, force, ultrasonic power, and time to attach two metallic materials, a wire, and a bond pad. In electronics, gold-aluminium (Au-Al) contact wire bonds are widespread due to corrosion resistance and great conductivity of both metals. However, due to the large contact-potential difference, the intermetallic compound growth at the metal’s interaction boundary has considerably worsened the advantageous properties of Au-Al intermetallic system. This intermetallic exhibit low toughness, and possibly low corrosion resistance, which would result in poor bonding quality. In this work, the materials used are 4x8 aluminium substrates and a 100-meter-long gold wire spool. This study aims to investigate the most optimised set of parameters to be used in Au-Al wire bond system, due to how problematic this system could have towards bonding quality. The experimental array was created using a response surface methodology (RSM)-based design of experiments. The effect of parameters and their significance to bonding quality in the Au-Al bond system were studied using analysis of variance (ANOVA). A correlation model was created for the wire bond strength data. The findings suggest that, within the range of parameters examined, the proposed correlation model can be utilized to predict performance measures. The optimum value of Au-Al wire bond system parameters was established at the time of bond at the first bonding site selected for 300 milliseconds (ms), wire looping height selected for 1200 micrometre (μm), wire bond Y-axis length selected for 996 micrometre (μm), and ultrasonic force at second bonding site selected for 300 milli Newton (mN). The outcomes of this research add to our understanding of the Au-Al wire bonding contact, in addition, to enhancing the wire bond's quality.

A Probabilistic Bayesian Machine Learning Framework for Comprehensive Characterization of Bond Wires in IGBT Modules Under Thermomechanical Loadings

A Probabilistic Bayesian Machine Learning Framework for Comprehensive Characterization of Bond Wires in IGBT Modules Under Thermomechanical Loadings

FOWLP and Flip Chip Cost Comparison: Impact of the Supply Chain Crunch

The impact of the pandemic on the semiconductor and electronics packaging supply chains has been in the news for over a year now. Current projections suggest the supply chain crunch could impact various industries through 2022 and 2023. While there are many ramifications of this shortage, one is certainly the impact on cost. Pricing for packages built with more mature technologies, such as wire bond and flip chip, has changed dramatically. Both of these mature technologies have typically been seen as lower cost options than newer technologies, such as fan-out wafer level packaging (FOWLP). Due to the recent shortages, the cost comparison is no longer as straight-forward as it was before. This paper will analyze the cost of building various packages using flip chip, wire bond, and FOWLP technologies. Factory overhead, indirect costs, and profit margins will be taken into account to turn this into a price comparison, rather than just a comparison of direct costs. The analyses will include the price of a package built using FOWLP technology, the price of flip chip and wire bond packages built before recent supply chain disruptions, and the new expected prices of flip chip and wire bond packages. Activity based cost modeling will be used for this analysis. This is a bottom-up, detailed approach to cost that accounts for the many cost components associated with every step of the process flow, such as material, labor, and capital depreciation. The goal of this analysis is to understand how supply chain disruptions have changed the cost parity points of wire bond, flip chip, and FOWLP packages.