Wire Bond Research Articles

Ionic charge distributions in silicon atomic surface wires.

Using a non-contact atomic force microscope (nc-AFM), we examine continuous dangling bond (DB) wire structures patterned on the hydrogen terminated silicon (100)-2 × 1 surface. By probing the DB structures at varying energies, we identify the formation of previously unobserved ionic charge distributions which are correlated to the net charge of DB wires and their predicted degrees of freedom in lattice distortions. Performing spectroscopic analysis, we identify higher energy configurations corresponding to alternative lattice distortions as well as tip-induced charging effects. By varying the length and orientation of these DB structures, we further highlight key features in the formation of these ionic surface phases.

Стабилизация сварочного усилия в процессе ультразвукового монтажа проволочных и ленточных выводов

To improve the quality of ultrasonic wire and ribbon bonding, the author propose a methodology for stabilizing the bonding force by compensating the rigidity of ultrasonic transducer (UST) mount in the ultrasonic / thermosonic bonding cycle. The author analyze the construction of ultrasonic technological systems and factors affecting the stability of the bonding process. The bonding force is controlled by an electromagnetic unit based on a coil in the field of a constant magnet, the force being directly proportional to the flowing current in the coil. The rigidity of ultrasonic transducer mount was compensated by the data obtained during the preliminary calibration of the change in the mount force over the entire UST overrun range. The calibration in this case is performed with no current flowing through the coil. The force value can be picked up from a digital force sensor. The force values are simultaneously compared with the digitized signal of the deformation sensor. The obtained data is stored in the memory of the wire bonder. In the bonding cycle, after the moment of contact is determined, the drive unit moves the bonding head vertically by the value of a predetermined distance of approximately one diameter of the bonding wire. This causes the movable part of the UST mount to rise and the force to increase. This increase is compensated by the automatic reduction of the current in the electromagnetic coil, which allows maintaining the preset force at the specified level. The bonding force during bonding is compensated in the same way, with the difference that the vector of force compensation changes – the force should increase with an increase in the deformation of the bonding wire. The implementation of the proposed algorithm made it possible to improve the bonding force stabilization to 20% when bonding thick wire, as well as to improve bonding quality. The proposed solution is also applicable in other technological ultrasound bonding systems, including bonding wire with the diameter of <100 microns.

Study on Ultrafine Wire Bonding and Performance of Radio Frequency Devices

Study on Ultrafine Wire Bonding and Performance of Radio Frequency Devices

Application of Creep Multi-linear Rule to ORNL Modified Strain Hardening of Al Wire Bonding in Power Module

Application of Creep Multi-linear Rule to ORNL Modified Strain Hardening of Al Wire Bonding in Power Module

Accelerated reliability testing of Cu-Al bimetallic contact by a micropattern corrosion testing platform for wire bond device application

Accelerated reliability testing of integrated circuit (IC) packages, such as wire-bonded devices, is a useful tool for predicting the lifetime corrosion behavior of real-world devices. Standard tests, such as highly accelerated stress test, involves subjecting an encapsulated device to high levels of humidity and high temperature (commonly 85–121 ⁰C and 85–100% relative humidity). A major drawback of current reliability tests is that mechanistic information of what occurs between t = 0 and device failure is not captured. A novel method of in-situ investigation of the device corrosion process was developed to capture the real time mechanistic information not obtained in standard reliability testing [1]. The simple, yet effective methodology involves:•Immersing a micropattern or device directly into contaminant-spiked aqueous solution, and observing its morphological changes under optical microscope paired with a camera.•Short (2–48 h) time required for testing (compared to 24–300 h of standard tests).•No need for humidity chambers.

Connecting Chips With More Than 100 GHz Bandwidth

Connecting chips within a module is a basic requirement in transforming MMIC performance to system functionality. More and more applications demand for operation at high mm-wave frequencies or with ultra-large bandwidth. While semiconductor devices have seen tremendous progress in terms of their frequency limits, the chip interconnects lag behind and often form the bottleneck in realizing such systems. This paper reviews the broadband potential of the most common interconnect types in use and their performance demonstrated so far, covering wirebonding, approaches with chips embedded in a substrate, and flip-chip. Additionally, as an intermediate solution between system-on-chip and system-in-a-package, semiconductor hetero-integration on the chip-level is included. As is discussed, bond wire interconnects are most limited in bandwidth among the four types and reach the 100 GHz band only at the expense of narrowband characteristics. Dedicated embedded-chip packaging techniques show significantly better performance, bandwidths in the order of 100 GHz have been shown in the literature. Flip-chip has clearly the highest potential, interconnects covering the range from DC to 500 GHz have been demonstrated and are presented in the paper. Hetero-integration on the chip proves to allow for very broadband interconnects between elements and circuits on the compound chip as well: For an InP-on-BiCMOS process 325 GHz bandwidth were achieved and even higher values seem to be feasible.

Effect of Temperature on Strain-Induced Hardness of Lead-Free Solder Wire using Nanoindentation Approach

Hardness properties of SAC305 solder wire under tensile test at varied temperature was investigated. Continuous multi-cycle (CMC) nanoindentation technique with ten cycle of indentation for each sample was performed to evaluate the hardness behaviour of SAC305 solder wire at different depth of indentation. As a result, all investigated SAC305 solder wire under constant strain rate of tensile test and at different temperature revealed the occurrence of indentation size effect (ISE). At initial cycle of indentation, SAC305 solder wire at room temperature (25 °C) have higher hardness value compared to the others sample which exposed to the varied temperature during tensile test. Besides, higher temperature causes the higher strain or elongation to the SAC305 solder wire. Applied of strain during the tensile test had generated the pre-dislocation activity in the SAC305 solder wire. Therefore, higher hardness values of SAC305 at room temperature is due to the existence of high dislocation density induced by the applied strain. Nevertheless, the existence of heat at 60, 90, 120 and 180 °C during the tensile test prompt the rearrangement of dislocation and reduce the dislocation activities, thus, allowing higher elongation of solder wire.

Effect of Ceramic Capillary Parameters on Bonded Morphology and Strength.

The effects of the geometry parameters of a ceramic cleaver on the morphology of ball and second bonded points were studied using an automatic wire bonder, push pull tester, scanning electron microscope, ceramic capillary with different geometric parameters and φ25.4 μmAg-5Au bonding alloy wire, etc. The result shows that when the inner hole diameter (IHD) of the ceramic capillary is 1.3 times the diameter of the alloy wire (33 μm), the neck morphology of the ball bonded point (first bonded point) meet the requirements. The neck of the ball bonded point appeared to fracture when the IHD is 26 μm; The neck of the ball bonded point appeared as an irregular shape when the IHD is 41 μm. When the inner cutting angle diameter (ICAD) is 64 μm, the size of the mashed ball diameter (MBD) is qualified. When the ICAD is 51 μm, the MBD is too large and mashed ball overflows the pad. When the ICAD is 76 μm, the ball bonded point is too high. When the inner cutting bevel angle (ICBA) is 100°, the MBD size meets the requirements of the pad. When the ICBA was reduced to 70°, the ball bonded point is eccentric. When the ICBA was increased to 120°, the MBD is too large and is connected to the adjacent pad contact. The size of the fish tail of the second bonded point (second bonded point) changed in the same direction as the tip diameter (TD) changes. When the TD is 178 μm, the fish tail shape is regular and symmetrical. When the working face angle (WFA) is 8° and the outer circular radius (OCR) is equal to the diameter of the alloy wire (25.4 μm), the fish tail shape is regular. When the WFA is higher than 11° or the OCR is higher than 30 μm, the fish tail will appear as virtual welding, and when the WFA is less than 4°, the fish tail of the second bonded point will break due to thinning. When the OCR is less than 20 μm, the fish tail of the second bonded point is too long and causes a short circuit.

Proton strings and rings in atypical nucleation of ferroelectricity in ice

Ordinary ice has a proton-disordered phase which is kinetically metastable, unable to reach, spontaneously, the ferroelectric (FE) ground state at low temperature where a residual Pauling entropy persists. Upon light doping with KOH at low temperature, the transition to FE ice takes place, but its microscopic mechanism still needs clarification. We introduce a lattice model based on dipolar interactions plus a competing, frustrating term that enforces the ice rule (IR). In the absence of IR-breaking defects, standard Monte Carlo (MC) simulation leaves this ice model stuck in a state of disordered proton ring configurations with the correct Pauling entropy. A replica exchange accelerated MC sampling strategy succeeds, without open path moves, interfaces, or off-lattice configurations, in equilibrating this defect-free ice, reaching its low-temperature FE order through a well-defined first-order phase transition. When proton vacancies mimicking the KOH impurities are planted into the IR-conserving lattice, they enable standard MC simulation to work, revealing the kinetics of evolution of ice from proton disorder to partial FE order below the transition temperature. Replacing ordinary nucleation, each impurity opens up a proton ring generating a linear string, an actual FE hydrogen bond wire that expands with time. Reminiscent of those described for spin ice, these impurity-induced strings are proposed to exist in doped water ice too, where IRs are even stronger. The emerging mechanism yields a dependence of the long-time FE order fraction upon dopant concentration, and upon quenching temperature, that compares favorably with that known in real-life KOH doped ice.

A Novel Bond Wire Fault Detection Method for IGBT Modules Based on Turn-on Gate Voltage Overshoot

Bond wire degradation is one of the most common failure modes for wire-welded packaging insulated-gate bipolar transistor (IGBT) modules. This article proposes a novel bond wire detection method based on IGBT turn-on gate voltage overshoot. The degree of bond wires lift-off will change the stray inductance of the gate charge loop circuit, and therefore has a strong influence on turn-on gate voltage overshoot before miller platform, which can be used as an effective bond wire fault indicator. A double pulse test platform is built to verify the resolution and sensitivity of the proposed precursor for bond wire degradation. The dependences on bus voltages, load currents, junction temperatures are discussed and tested. The experimental results show that the gate turn-on voltage overshoot of IGBT increases with the increasing severity of bond wire faults, which agrees with the theoretical analysis. The proposed turn-on gate voltage overshoot-based method has a high sensitivity for identifying bond wire fault at the incipient stage. It offers an effective technique for detecting bond wire degradation for practical applications.

Aging Diagnosis of Bond Wire Using On-State Drain-Source Voltage Separation for SiC MOSFET

Bond wire aging is a universal failure form of silicon carbide metal-oxide-semiconductor field-effect transistor (SiC MOSFET) module. Real-time condition monitoring of bond wire is an important guarantee for the stable operation of power electronics system. In this article, a method of monitoring the aging state of bond wire in SiC MOSFET module using on-state drain-source voltage (OSDSV) separation technique is proposed. Firstly, the temperature dependence of the conduction circuit resistance from drain terminal to source terminal in SiC MOSFET module is analyzed to obtain the temperature characteristics of the OSDSV. Secondly, the resistance of the package structure in SiC MOSFET module is extracted, and the OSDSV is divided into two parts: the package structure voltage and the chip OSDSV, and the analytical model for estimating the junction temperature of SiC MOSFET module in the healthy state is acquired. Finally, the package structure voltage is employed to monitor the aging degree of bond wire in SiC MOSFET module, and the flow chart of aging diagnosis of bond wire is established. The proposed method can accurately identify the failure state of bond wire lift-off. Theoretical and experimental results prove that the method is feasible.

Automated on-axis direct laser writing of coupling elements for photonic chips.

Direct laser writing (DLW) has recently been used to create versatile micro-optic structures that facilitate photonic-chip coupling, like free-form lenses, free-form mirrors, and photonic wirebonds. However, at the edges of photonic chips, the top-down/off-axis printing orientation typically used limits the size and complexity of structures and the range of materials compatible with the DLW process. To avoid these issues, we develop a DLW method in which the photonic chip's optical input/output (IO) ports are co-linear with the axis of the lithography beam (on-axis printing). Alignment automation and port identification are enabled by a 1-dimensional barcode-like pattern that is fabricated within the chip's device layer and surrounds the IO waveguides to increase their visibility. We demonstrate passive alignment to these markers using standard machine vision techniques, and print single-element elliptical lenses along an array of 42 ports with a 100 % fabrication yield. These lenses improve fiber-to-chip misalignment tolerance relative to other fiber-based coupling techniques. The 1 dB excess loss diameter increases from ≈ 2.3 μm when using a lensed fiber to ≈ 9.9 μm when using the DLW printed micro-optic and a cleaved fiber. The insertion loss penalty introduced by moving to this misalignment-tolerant coupling approach is limited, with an additional loss (in comparison to the lensed fiber) as small as ≈1 dB and ≈2 dB on average. Going forward, on-axis printing can accommodate a variety of multi-element free-space and guided wave coupling elements, without requiring calibration of printing dose specific to the geometry of the 3D printed structure or to the materials comprising the photonic chip. It also enables novel methods for interconnection between chips. To that end, we fabricate a proof-of-concept 3D photonic wire bond between two vertically stacked photonic chips.

Stitch-bond reliability evaluation by construction analysis

Electronic components have changed the way we live and the way we use technology since they were first introduced into products. Most equipment is only as reliable as its internal electronic components. In electronic integrated circuit (IC) components, wire bonding is the most common first-level interconnection method between die and lead. Failure of wire bonds can have very costly consequences in the severe or harsh operating conditions of the oil and gas industry, where services such as rig charge are extremely expensive.Wire bonding has several failure modes and mechanisms. The most common failure modes are ball bond failure due to intermetallic growth and stress, wire rupture due to electrical overstress, and stitch-bond related failures due to repeated flexure of the wire induced by thermomechanical loading. The ball and stitch-bond failures are accelerated in harsh environment applications.This study focuses on gold (Au) and copper (Cu) stitch-bond failures caused by mechanical vibration coupled with thermal cycling of gull-wing plastic components. Both design and operating parameters impact stitch-bond reliability. In this study, simulation was used first to identify the potential effect of design parameters (component level and assembly level) on the stress magnitude and to rank the most critical structural parameters impacting stitch-bond reliability. Test units were designed based on the simulations and subjected to the test conditions that provided feedback to the model to define acceptance criteria using experimental results. Destructive construction analysis confirmed the location of stitch-bond failures and variables contributing to early failure or extended life of stitch bonds. This paper describes the component robustness prediction method that can be used as a lot acceptance test to screen plastic encapsulated IC components using construction analysis.

Thermo-Mechanical Stress Comparison of a GaN and SiC MOSFET for Photovoltaic Applications

Integrating photovoltaic applications within urban environments creates the need for more compact and efficient power electronics that can guarantee long lifetimes. The upcoming wide-bandgap semiconductor devices show great promise in providing the first two properties, but their packaging requires further testing in order to optimize their reliability. This paper demonstrates one iteration of the design for reliability methodology used in order to compare the generated thermo-mechanical stress in the die attach and the bond wires of a GaN and SiC MOSFET. An electro-thermal model of a photovoltaic string inverter is used in order to translate a cloudy and a clear one-hour mission profile from Arizona into a junction losses profile. Subsequently, the finite element method models of both devices are constructed through reverse engineering in order to analyze the plastic energy. The results show that the plastic energy in the die attach caused by a cloudy mission-profile is much higher than that caused by a clear mission-profile. The GaN MOSFET, in spite of its reduced losses, endures around 5 times more plastic energy dissipation density in its die attach than the SiC MOSFET while the reverse is true for the bond wires. Potential design adaptations for both devices have been suggested to initiate a new iteration in the design for reliability methodology, which will ultimately lead to a more reliable design.

Gold wire bond study for automotive application

In this publication, the influence of bond wire material properties (Au 2N/4N), and plasma pre-treatment on the wire-bond strength is investigated based on Automotive Electronics Council Qualification (AEC-Q100) and customer requirements. The wire pull force capability is compared, and growth of the Au/Al intermetallic phase (IMP) is analyzed with scanning electron microscope (SEM) cross sections after High Temperature Storage Life (HTSL, 150 °C), Temperature Cycling (TC, −65 °C – 150 °C) and unbiased Humidity Accelerated Stress Test (uHAST, 130 °C/85% relative humidity (RH)). The effect of plasma treatment prior bonding on 2N and 4N wires is discussed and compared to the results without plasma treatment prior wire bonding. Furthermore, test acceleration by using elevated test temperatures (HTSL, 250 °C) is shown and the wire capability compared.

Using of bond-wire resistance as aging indicator of semiconductor power modules

This paper investigates the use of wire—bonds contact resistance as indicator to diagnose the health state of power electronics modules. This technique is especially dedicated to monitoring the degradation of the topside interconnection (metallization-wire bonds) when the module is wired with a Kelvin point. One advantage of this indicator is that it can be followed online, without being disturbed by current or voltage, to diagnose the state of health and, possibly, the prognosis of the remaining lifetime of the power module by associating it with a lifetime model. For this purpose, based on power-cycling tests in different conditions, a comparison between this indicator and the one commonly used, i.e. the collector-emitter voltage Vce, shows that the first one is much more sensitive to the degradations, easier to use online and finally should be more suitable for lifetime prognosis.

Mathematical Modelling of Low Temperature Solder Direct Extrusion

Defining of process technological parameters is very important for low temperature solder extrusion. A mathematical model of low temperature solder wire and rods direct extrusion, which allows determining the energy-power process parameters, has been developed. The validation of the mathematical model for adequacy was checked during a laboratory experiment on a hydraulic press. In laboratory the force and speed of pressing were measured and recorded using the data collection system installed on it. The validation of the model for adequacy was carried out by pressing 08.00 and 015 mm rods and 02.00 mm wire and showed fine precision of calculations with experimental measurements. The error did not exceed 10%. The resulting mathematical model was used for analytical studies of Sn-In alloy bars and wires direct pressing technological modes. Calculations have shown that a decrease in the finished rod (wire) diameter from 16.00 to 2.00 mm while maintaining the workpiece size 030.00 mm leads to an increase in the pressing force from 86 kN to 131 kN at the initial moment of pressing. It increases the elongation ratio from 4 to 256. The pressing force of 08.00 mm rod increases from 25 to 171 kN after an increase in the diameter of the workpiece from 12.0 to 40.0 mm. Analytical studies on the model showed that it is possible not only to study the pressing process in order to understand the mechanisms of forming the mechanical and operational properties of the finished rod (wire), but also to design resource-saving pressing modes for various product gauges, to carry out substantiated selection of the required equipment and accessories.

Effects of alloying elements in high reliability copper wire bond material for high temperature applications

Recently, a shift from Au bonding wire to Cu bonding wire is expected for automotive application. Palladium coated copper (PCC) wire is strong candidate since it is widely used in LSI packages owing to its high performance and low cost. In order to apply PCC wire to automotive devices, long-term reliability specific to automobiles including stable operation under harsh environment with high temperature and humidity is required. However, pitting corrosion at the wedge bond portion was reported with PCC wire under high temperature storage life (HTSL) test. Depending on the surrounding environment such as mold compound, it is difficult for conventional PCC wire to achieve the target of automotive application. A newly developed PCC wire (EX1R) has thus developed. By using additive element in Cu core, halide induced interface corrosion and also pitting corrosion can be prevented successfully. In this paper, effect of additive element on the corrosion resistance will be discussed. The result shows that additive element forms protective passivation layer on the intermetallic compound (IMC) and Cu surface. Thereby, EX1R improves bond reliability even under severe reliability test condition.

Analysis of the aging mechanism occurring at the bond-wire contact of IGBT power devices during power cycling

This paper focuses on the degradation at the wire bond contact with the metalized pad, and precisely its evolution with the power module aging. In order to induce damage in this particular zone, an accelerated power cycling test is carried out on well-suited devices. The on-state voltage (VCE) is measured during the test as an indicator of the degradation in the wire and metallization. Then, analyses of the interface wire-metallization are done with a numerical microscope and the EBSD (Electron Back-Scattered Diffraction) technique. As a result, an attempt to correlate the evolution of the degradation with the changes in the granular microstructure of the aluminium constituting the wire and metallization is proposed.

An Optimized Ag–5Pd–3.5Au Bonding Wire for the Resistance of Ag Ion Migration in LED Packages

The bondability and reliability of Ag–5Pd–3.5Au alloy wire was verified previously for application in light-emitting diode (LED) packages. This Ag-alloy bonding wire has an electrical resistivity of 4.6 $\mu \Omega \cdot $ cm, lower than those of the ternary Ag–3Pd–20Au (8.6 $\mu \Omega \cdot $ cm) and Ag–3Pd–8Au wires (5.0 $\mu \Omega \cdot $ cm). Further evaluation of the resistance of ion migration in Ag-alloy bonding wires using water drop tests indicated that a declining tendency of ion migration rates existed for various binary Ag–Pd and ternary Ag–Pd–Au alloy wires with increases in Pd and Au contents. Among the all Ag-alloy bonding wires in this study, the Ag–5Pd–3.5Au wire exhibited the lowest ion migration rate of 4.87 $\mu \text{m}$ /s. The measurements of anodic dissolution rates were consistent with the tendency of ion migration rates, which were dependent on Pd and Au contents, resulting in the low value of Ag–5Pd–3.5Au alloy wire (0.017 $\mu \text{m}$ /s).