Predicted Stresses in Wire Bonds of Plastic Packages During Transfer Molding

1991 ◽  
Vol 113 (1) ◽  
pp. 16-20 ◽  
Author(s):  
E. Suhir ◽  
L. T. Manzione
Keyword(s):  
Integrated Circuit ◽  
Stress Model ◽  
Ball Bond ◽  
Transfer Molding ◽  
Plastic Packages ◽  
Wire Bond ◽  
Wire Bonds ◽  
Plastic Package ◽  
Induced Stresses ◽  
The Wire

An analytical stress model is developed for the evaluation of flow induced stresses in wire bonds of plastic packages during molding. We limit our analysis to the stresses acting in the plane of a wire bond. These stresses can possibly result in liftoff of the ball bond from the bonding pad of the integrated circuit. The main purpose of the analysis is to evaluate the effect of the wire bond configuration. It is shown that the stresses in wire bonds are proportional to the square of the ratio of the wire-bond span to the diameter of the wire. This explains the difficulty in molding assemblies with long wire bond spans. We also showed that wire configurations, characterized by nonzero slope angles at the ends, result in lower stresses than conventional wire shapes, where the wedge bond to the electric lead forms a zero angle. The obtained results are useful when designing plastic package assemblies and/or choosing the appropriate wire bond loop height and span.

Effects of ball bond diameter on wire bond reliability for automotive application

2016 ◽  
Vol 33 (1) ◽  
pp. 53-60 ◽  
Author(s):  
Hui Yuen Peng ◽  
Mutharasu Devarajan ◽  
Teik Toon Lee ◽  
David Lacey
Keyword(s):  
Isothermal Aging ◽  
Production Costs ◽  
Automotive Application ◽  
Comsol Multiphysics ◽  
Ball Bond ◽  
Content Type ◽  
Wire Bond ◽  
Wire Bonds ◽  
Ball Bonds ◽  
The Wire

Purpose – The purpose of this paper is to investigate the reliability of wire bonds with three varying ball bond diameters, which are ball bonded with three different sizes of gold wires in light-emitting diode (LED) package under high-temperature environment. In automotive applications, “lifted ball bond” issue is a potential critical point for LED device reliability, as the wire bonds are usually stressed under high operating temperature during their lifetime. Moreover, the reliability of wire bonds in recent LED production has fallen under scrutiny due to the practice of reducing wire diameters to cut down production costs. Design/methodology/approach – Three gold wires with sizes of 2, 1.5 and 1 mm were ball bonded on the LED chip bond pad via thermosonic wire bonding method to produce three different ball bond diameters, that is, 140, 120 and 100 μm, respectively. The reliability of these wire bond samples was then studied by performing isothermal aging at 200°C for the time interval of 30, 100 and 500 hours. To validate hypotheses based on the experimental data, COMSOL Multiphysics simulation was also applied to study the thermal stress distribution of wire bond under an elevated temperature. Findings – Experimental results show that the interfacial adhesion of wire bond degrades significantly after aging at 200°C for 500 hours, and the rate of interfacial degradation was found to be more rapid in the wire bond with smaller ball bond diameter. Experimental results also show that ball bonds randomly elongate along an axis and deforms into elliptical shapes after isothermal aging, and ball bonds with smaller diameters develop more obvious elongations. This observation has not been reported in any previous studies. Simulation results show that higher thermal stress is induced in the wire bond with the decrease of ball bond diameter. Practical implications – The reliability study of this paper provides measurements and explanation on the effects of wire diameter downsizing in wire bonds for automotive application. This is applicable as a reliability reference for industries who intend to reduce their production costs. Other than that, the analysis method of thermal stresses using COMSOL Multiphysics simulations can be extended by other COMSOL Multiphysics users in the future. Originality/value – To resolve “lifted ball bond” issue, optimization of the bond pad surface quality and the wire bond parameter has been studied and reported in many studies, but the influence of ball bond diameter on wire bond reliability is rarely focused. Moreover, the observation of ball bonds randomly elongate and deform more into elliptical shape, and ball bond with smaller diameter has the highest elongation after isothermal aging also still has not been reported in any previous studies.

Response of Long Sculpted Wire Bonds to Vibrational Excitation

2012 ◽  
Vol 2012 (1) ◽  
pp. 000665-000676
Author(s):  
Thomas F. Marinis ◽  
Joseph W. Soucy
Keyword(s):  
Finite Element ◽  
Vibrational Excitation ◽  
Capacitive Coupling ◽  
Finite Element Models ◽  
Wire Length ◽  
Resonant Frequencies ◽  
Simple Loop ◽  
Wire Bond ◽  
Wire Bonds ◽  
The Wire

The pitch of wire bond connections is decreasing to meet the need for higher interconnect densities, while at the same time, the ratio of wire length to diameter is increasing, which lowers the mechanical resonant frequency of the wire. In many applications in which MEMS sensors are coupled with ASIC front end electronics, the bonded wires can be subjected to a wide frequency spectrum of mechanical vibrations. One potential consequence is that the parasitic capacitances of the sensor could vary dynamically at a magnitude comparable to that of the sensor signal. In extreme cases, intermittent shorts or fatigue failures of the wire bonds could occur. A recent paper by Barber et. al, showed that wire bonds carrying alternating currents in a strong magnetic field could suffer fatigue failure.[1] Their analysis and experiments focused on simple loop geometries. In many applications, more complex wire bond geometries are used to minimize loop height and obtain dense wiring in stacked chip configurations. These geometries give rise to many more vibration modes with unique resonant frequencies and displaced shapes. We have used simple analytical beam models in conjunction with finite element models (FEM) to study various wire bond configurations subject to mechanical vibratory excitation. We focused on the effects of overall wire length and geometric shape on resonant modes. The finite element models were also used to calculate the capacitance between adjacent wires subject to mechanical excitation at one or more of their resonant frequencies. We show that there is an apparent shift in the time averaged capacitive coupling that increases with increasing vibration amplitude.

Predicted Residual Bow of Thin Plastic Packages of Integrated Circuit Devices

1992 ◽  
Vol 114 (4) ◽  
pp. 467-470 ◽  
Author(s):  
E. Suhir
Keyword(s):  
Integrated Circuit ◽  
Effective Means ◽  
Thermal Contraction ◽  
Element Solution ◽  
Printed Wiring Board ◽  
Thermally Induced ◽  
Plastic Packages ◽  
Plastic Package ◽  
Thin Plastic ◽  
Wiring Board

Thin plastic packages are prone to residual bows caused by the thermal contraction mismatch of the constituent materials: silicon (chip), metal (leadframe), and epoxy (encapsulant). Since excessive bow can make normal mounting of a plastic package on a printed wiring board difficult, it is important that such a bow can be predicted, minimized, and, if possible, avoided. Accordingly, in this analysis we develop a simple and easy-to-apply calculation method for the prediction of the residual thermally-induced bow in a thin elongated plastic package. We use the obtained formula for the curvature to determine whether the chip/leadframe assembly can be positioned within the epoxy encapsulant in such a way that no residual bow occurs. We show that employment of epoxy encapsulants with elevated coefficients of thermal expansion can be an effective means to reduce the bow, and that application of thin and/or low expansion leadframes is also desirable. The calculated bow, obtained for a 1mm thick, 14mm long package, agrees satisfactorily with the finite-element solution. The results of our analysis can be utilized as a guidance in the evaluation of the expected bow, as well as for a rational physical design of thin plastic packages.

Finite Element Analysis of Copper Wire Bonding in Integrated Circuit Devices

2012 ◽  
Vol 566 ◽  
pp. 293-299 ◽  
Author(s):  
Nauman Dastgir ◽  
Pooria Pasbakhsh ◽  
Ning Qun Guo ◽  
Norhazlina Ismail ◽  
Kheng Lim Goh
Keyword(s):  
Finite Element ◽  
Integrated Circuit ◽  
Copper Wire ◽  
Bonding Temperature ◽  
Element Analysis ◽  
Appreciable Change ◽  
Bonding Force ◽  
Wire Bond ◽  
Aluminum Metallization ◽  
Induced Stresses

Axisymmetric finite element models of copper wire-bond-pad structure for an integrated circuit devicewere developed to investigate theeffects of bonding force, initial bonding temperature, Aluminum metallization thickness, bond pad thickness and free air ball (FAB) diameter on induced stresses in the wire-bond structure. The results show that an increase in bonding force greatly increased the induced stresses in the copper FAB and bond pad (aluminum and silicon). However, a change in bonding temperature while keeping the bonding force constant does not result in an appreciable change in the stress. Similarly an increase in aluminium metallization thickness does not yield appreciable variation in the stress and strain in the bond pad. Over the range of FAB diameters studied it is found that bigger FAB yields smaller stress in the overall structure

Effects of Stacked Layers and Stacked Configurations on Wire Sweep and Wire Sag of Advanced Overhang/Pyramid Stacked Packages

2017 ◽  
Vol 139 (4) ◽  
Author(s):  
Huang-Kuang Kung ◽  
Chi-Lung Hsieh
Keyword(s):  
Semiconductor Industry ◽  
Central Segment ◽  
Center Region ◽  
Wire Bond ◽  
Wire Bonds ◽  
Straight Portion ◽  
Selection For ◽  
The Wire

Overhang and/or pyramid stacked packages are the trend in the semiconductor industry. As the stacked layers increase drastically, the wire sweep and wire sag problems become more and more serious. Based on some types of frequently used stacked configurations, their corresponding wire sweep and wire sag stiffness and deflections are investigated for extra-high stacked layers. Two typical profiles of Q_loop and S_loop wire bonds are included in this study. However, wire sweep and wire sag have to be considered in two different design aspects. For wire sweep, we have the conclusion that the maximum wire sweep deflections always occur near the central segment of a wire bond. As for the wire sag, the maximum wire sag may take place in the center region of the straight portion of a wire bond. The result shows that the deflections of wire sag can be reduced significantly by simply shifting the position of the kink or bend created within a wire bond. Finally, we have concluded that a stacked configuration with smallest bond span may be the preferred selection for the concerns of wire sweep and wire sag issues.

Effects of Bond Pad Thickness on Shear Strength of Copper Wire Bonds

2017 ◽  
Vol 2017 (HiTEN) ◽  
pp. 000068-000073 ◽  
Author(s):  
Subramani Manoharan ◽  
Chandradip Patel ◽  
Stevan Hunter ◽  
Patrick McCluskey
Keyword(s):  
Shear Strength ◽  
Shear Test ◽  
Failure Modes ◽  
High Reliability ◽  
Copper Wire ◽  
Test Method ◽  
Ball Bond ◽  
Wire Bond ◽  
Industry Standards ◽  
Wire Bonds

Abstract Copper (Cu) wire bonding is now widely accepted as a replacement for gold (Au), however, its use in high reliability applications is limited due to early failures in high temperature and humid conditions. The Au to Cu wire transition is mainly driven by cost savings though there are other advantages to Cu such as better electrical and thermal conductivity, slower intermetallic compound (IMC) formation and reduced wire sweep during transfer molding. Some automotive, industrial and aerospace industries are still reluctant to adopt Cu wire bonded products due to perceived risks of wire and bond pad cracks, the potential for corrosion, and some lack of understanding about its reliability in harsh conditions. A wire bond is considered good if destructive sampling qualification tests and periodic monitors pass for the batch. Tests include wire pull strength, wire bond shear, IMC coverage, and thickness of bond pad aluminum (Al) remaining beneath the bond. Nondestructive inspections also verify acceptable ball diameter and Al “splash”. This paper focuses on the bond shear test and its contribution to Cu ball bond reliability assessment, especially when changing Al bond pad thickness. A new revision of the JEDEC Wire Bond Shear Test Method, JESD22-B116B, has just been released, to include Cu wirebonds for the first time. It helps to clarify shear test failure modes for Cu ball bonds. However, there are still questions to be answered through research and experimentation, especially to learn the extent to which one may predict Cu ball bond reliability based on shear test results. Pad Al thickness is not considered in the current industry standards for shear test. Yet bond pad Al thickness varies widely among semiconductor products. This research is intended to contribute toward improved industry standards. In this study, power and time bonding parameters along with bond pad thickness are studied for bond strength. Several wire bonds are created at different conditions, evaluated by optical microscope and SEM, IMC% coverage and bond shear strength. Similar bonding conditions are repeated for bond pads of 4um, 1um and 0.5um thickness.

scholarly journals Bond strength evaluation of heat treated Cu-Al wire bonding

2018 ◽  
Vol 12 (4) ◽  
pp. 4275-4284
Author(s):  
S. Shariza ◽  
T. Joseph Sahaya Anand ◽  
A. R. M. Warikh ◽  
Lee Cher Chia ◽  
Chua Kok Yau ◽  
...  
Keyword(s):  
Bond Strength ◽  
Bonding Temperature ◽  
Wire Bonding ◽  
Strength Evaluation ◽  
Wire Bond ◽  
Wire Bonds ◽  
Transmission Electron ◽  
The Wire ◽  
Ball Shear Strength

Bond strength evaluation of wire bonding in microchips is the key study in any wire bonding mechanism. The quality of the wire bond interconnection relates very closely to the reliability of the microchip during performance of its function in any application. In many reports, concerns regarding the reliability of the microchip are raised due to formation of void at the wire-bond pad bonding interface, predominantly after high temperature storage (HTS) annealing conditions. In this report, the quality of wire bonds prepared at different conditions, specifically annealed at different HTS durations are determined by measurements of the strength of the interface between the bond wire and the bond pad. The samples are tested in pull test and bond shear test. It was observed that the higher bonding temperature as well as the longer duration of HTS increased the bond strength. This is represented through the analysis of the measurements of ball shear strength. This is due to the fact that higher bonding temperature and longer HTS promoted better growth of the Cu-Al IMC layer. A transmission electron microscopy - energy dispersive X-ray analysis (TEM-EDX) has been carried out to observe the formation of the Cu-Al IMC layer in the sample.    

On the Wire Sweep Experiments and Predictions of Gold Wire for Semiconductor Wirebonding Technology

2006 ◽  
Vol 505-507 ◽  
pp. 319-324
Author(s):  
Huang Kuang Kung ◽  
Bo Wun Huang
Keyword(s):  
Elevated Temperature ◽  
Drag Force ◽  
Material Properties ◽  
Gold Wire ◽  
Molding Process ◽  
Transfer Molding ◽  
Wire Bond ◽  
Temperature Environment ◽  
The Wire

This paper studies the elevated-temperature sweep characteristics of wire bond during transfer molding process for semiconductor package. A set of sweep experiments is also conducted to acquire the sweep stiffness of wire bond for several bond spans and bond heights. The results show the increase of the sweep deflections is more delicate to bond span than bond height. The main objectives of this research are to obtain elevated-temperature material properties of gold wire experimentally and to predict the wire sweep of various bond spans and bond heights subjected to drag force in the compound flow during transfer molding. Based on the analysis results of ANSYS, the effects of bond span and bond height on wire sweep in the elevated-temperature environment can be obtained. Then, the elevated-temperature deflections of wire sweep can be predicted.

Automated Wirepull Testing – Parallelogram of Forces-Real Time Application

2013 ◽  
Vol 2013 (1) ◽  
pp. 000331-000335
Author(s):  
Richard C. Garcia ◽  
Josef Sedlmair (F&K Delvotec)
Keyword(s):  
Real Time ◽  
High Density ◽  
Small Component ◽  
Manufacturing Operations ◽  
Wire Bond ◽  
Pull Strength ◽  
Wire Bonds ◽  
Optimum Position ◽  
The Wire ◽  
Pull Testing

In hybrid electronics, it is a standard practice to perform 100% wire bond pull testing to ensure robust wire bonding of the components. The principle behind Mil-STD-883 method 2023.5 compliant wire bond pull testing is to position the hook underneath the wire and either pull until the wire breaks or, alternatively, pull to a predefined force. With high density layouts, small component geometry or staggered wire bonds, it has been a challenge for manufacturing operations to maintain consistency in “manually” placing the wirepull hook on wires with varying height, looping profiles and wire distances. The influence of loop height and wire distance is a significant factor in determining the true wire pull strength. A low wire loop will result in lower measured pull strength, while a higher loop will result in higher pull strength. Therefore, if we can accurately quantify the loop height and profile then we can place the wirepull hook in the optimum position for pulling. In this study we will demonstrate how the “parallelogram of forces” can affect wirepull measurements. With the advent of the current generation of automated wirebond pull testers, we can accurately determine the appropriate correction factor(s) for varying loop heights in order to position the wirepull hook at the precise location necessary for accurate and meaningful results. In addition, with real time yield monitoring, the new pull testers are capable of locating and identifying missing wires that can often be attributed to the high density of today's circuit designs.

scholarly journals Predicting Fusing Current for Encapsulated Wire Bonds under Transient Loads

2010 ◽  
Vol 2010 (1) ◽  
pp. 000486-000493 ◽  
Author(s):  
Aditi Mallik ◽  
Roger Stout
Keyword(s):  
Single Pulse ◽  
Element Model ◽  
Current Response ◽  
Temperature Dependent ◽  
Wire Bonds ◽  
Potential Failure ◽  
Different Dimensions ◽  
Transient Loads ◽  
The Wire ◽  
Set Up

For high power IC chips, as device size inevitably decreases, the wire diameter unfortunately must decrease due to the need of finer pitch wires. Fusing or melting of wirebonds thus increasingly becomes one of the potential failure issues for such IC's. Experiments were performed under transient loads on dummy packages having aluminum, gold, or copper wires of different dimensions. A finite element model was constructed that correlates very well with the observed maximum operating currents for such wirebonds under actual experimental test conditions. A qualitative observation of typical current profiles, as fusing conditions were approached, was that current would reach a maximum value very early in the pulse, and then fall gradually. One goal achieved through the modeling was to show that the current in the wire falls with time due to the heating of the wire material. Correspondingly, the wire reaches the melting temperature not at the peak current but rather at the end of pulse. Further, modeling shows that knowledge of external resistance and inductance of the experimental set up are highly significant in determining the details of a fusing event, but if known along with the temperature-dependent wire properties, the simulation can predict the correct voltage and current response of the part with 2% error. On the other hand, lack of external circuit characteristics may lead to completely incorrect results. For instance, the assumption that current is constant until the wire heats to fusing temperature, or that current and temperature both rise monotonically to maximum values until the wire fuses, are almost certain to be wrong. The work has been carried out for single pulse events as well as pulse trains.

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