Thermosonic wire bonding process simulation and bond pad over active stress analysis february 2008 ieee transactions on electronics packaging manufacturing 311. Tail breaking is part of the standard bondoff process used on each wire bonder and produce a clean piece of wire with defined length tail suitable for subsequent fab formation. Wire bonding certification 3 days this three day course is a combination of classroom and handson exercises conducted at the wire bonder designed to teach the basics of manual gold ball and wedge wirebonding. This information was generated using two types of equipment. Wirebonding pressure temperature ultrasonic energy wire pad. Pure gold wire doped with controlled amounts of beryllium and other elements is normally used for ball bonding. Tips for increasing yields when wire bonding small mesa chips. This process brings together the two materials that are to be bonded using heat, pressure and ultrasonic energy referred to as thermosonic bonding. Nov 01, 2012 read modeling study of thermosonic flip chip bonding process, microelectronics reliability on deepdyve, the largest online rental service for scholarly research with thousands of academic publications available at your fingertips. Despite these potential advantages, it is rarely used besides ballwedge and gold wedgewedge applications, mostly due to. S designed to evaluate the combination of ultrasonic energy and thermocompression techniques, i. Hb1016 is a manual semiautomatic thermosonic wire bonder for wedge bonding, ball bonding and ball bumping.
It is followed by the cs in which a shift combined with ultrasonic friction is applied to remove the insulation layer. Gold to gold thermosonic bonding characterization of bonding parameters thi thuy luu1, hoangvu nguyen1. The wire bonding process in the package of mems accelerometer is analyzed by the finite element software ansyslsdyna. Effect of temperature on deformation characteristics of gold ball bond in aual thermosonic wire bonding gurbinder singh, othman mamat abstract wire bonding is a process that is used to form solidstate bonds to interconnect metals such as gold wires to metalized pads deposited on silicon integrated circuits.
Experimental and numerical study of the mechanical aspects. Wire bonding process is commonly used to interconnect chips to the outside world using gold wire since its inception in the mid 1950 using thermocompression, an application of heat and force. Finite element analysis on thermosonic ball bonding. Finite element analysis on thermosonic ball bonding process. This not only benefits the fine pitch of wire bonding capabilities, but also decreases the minimum wire bonding temperature required for the applied bonding force. Effect of efo parameters on cu fab hardness and work. Thermosonic flip chip tsfc bonding is a developing areaarray microelectronic package technology. Multiresponse optimisation has become an increasingly important issue in complex industrial processes, particularly in situations where more than one correlated responses must be assessed simultaneously. Wirebonding process wirebonding, or wire bonding, is the process of providing electrical connection between the silicon chip and the external leads of the semiconductor device using very fine bonding wires. Modeling study of thermosonic flip chip bonding process. Contents work shop wire bonding jan eite bullema introduction wire bonding 2 introduction equipment metallurgy shear testing process parameters demonstration in the lab 3. Copper wire is getting well accepted as a reliable design alternative to the gold wire in the wire bonding process. Typical wire bond process optimization small precision tools. Approximately 90% of all ic assembly in semiconductor packages is manufactured using gold ball bonding process, while aluminum wedge bonding is used to produce about 10% of other wire bonding requirements on printed circuit boards pcb, printed circuit.
Experimental study of kick up phenomenon in thermosonic wire. For this reason, several semiconductor companies are aiming to integrate copper wire bonding technology into their assembly lines. Many more reports were published in the nineties and some articles dedicated special emphasis to microwave and millimeter wave applications. Define ball and wedge bond specifications to be use as target response in optimizing a given application. Validated simulation of the ultrasonic wire bonding process.
Pdf development of a thermosonic wirebonding process. The strength of wire bond is evaluated through the bond pull test experiment. In this paper, a transient nonlinear dynamic finite element framework is developed, which integrates the wire bonding process and the silicon devices under bond pad. Microelectronic wire bonding with insulated au wire. The pull force obtained with a basic bonding process of insulated au wire and bare au wire are optimized by iteration and. Throughput also is an important factor, since it affects the cost of the device. Silver pick up during tail formation in thermosonic wire. Process quality improvement in thermosonic wire bonding. Thermosonic wire bonding process simulation and bond pad over. In this study, the loping process during wire bonding was recorded by using highspeed camera, and wire profiles evolution was obtained from images sequence by image processing method. The physics describing ultrasonic wire bonding is only partly known. Wire bond process parameters optimizing a wire bond process begins with a clear understanding of the machine setup, the response variables involved, and their relationship to one another.
Detailed descriptions and schematic drawings are given in, for example, references 1 4. Chavez sandia laboratories albuquerque, new mexico 87115 january 1976 abstract this study wfj. Alexander coucoulas is an american inventor, research engineer, and author. Influences due to the bonding process bonding machine.
Gold to gold thermosonic bonding characterization of. Bonding parameters such as ultrasonic power, ultrasonic generator current, electric flameoff current, firing time, bonding force, and temperature are discussed. Evaluation of wire bonding performance, process conditions. Several different experiments are performed on an automated thermosonic wire bonder with 25 m au and cu wires to investigate the efo process during ball bonding. Process quality improvement in thermosonic wire bonding by jaesik lee. Wirebonding is an electrical interconnection technique using thin wire and a combination of heat, pressure andor ultrasonic energy. Process advantages of thermosonic wedgewedge bonding using dosed tool heating abstract thermosonic wire bonding has a number of advantages over cold ultrasonic wire bonding. Pressure, temperature, and ultrasonic energy are combined to produce the bond. Cu wire bonding has been investigated for more than 25 years.
The bonding sequence is usually the same as that for the tc ballwedge process. The laser bonding process has developed to circumvent a high bonding force used for thermosonic bonding. Wire bonding process is commonly used to interconnect chips to the outside world using gold wire since its inception in the mid 1950 using thermocompression, an. The laser radiation is used to heat the tool tip during or immediately before the bonding process to heat wire and interface by thermal conduction and thus enable a thermosonic bond process.
Through detailed failure analysis and with the help of finite element analysis on stress simulation, the true root cause of. Challenges in the wire bonding process on enepig with regards to bondability and other plating related issues are summarized. To improve the bondability and ensure the reliability of aucu ball bonds of the thermosonic ts wire bonding process, an argonshielding atmosphere was applied to prevent the copper pad from oxidizing. High accuracy placement compared to smd solder process. Cu wire bonds have the limitations of high oxidation rate, high hardness, and susceptibility to corrosion. Solidstate microjoining mechanisms of wire bonding and flip. Au wire with a submicron thick insulation coating is bonded on standard ag plated leadframe diepads at 493 k. Basic wire bonding theory parameter development practical. The most common approach in thermosonic bonding is to ball bond to the chip, then stitch bond to the substrate.
In recent years, there are increasing research efforts in the quantitative understanding of the wire bonding process. Printed circuit boards pcbs were surface mounted prior to the wire bonding process with pbfree solder paste with water soluble organic acid oa flux. Simulation includes the ultrasonic transient dynamic bonding process and the stress wave transferred to bond pad device and silicon in the 1st bond. Process and equipment changes are needed for conversion to cu wire bonding, requiring.
Pdf thermosonic wire bonding process simulation and bond. The principal bonding process parameters such as bonding time, normal force, resonant frequency, ultrasonic power, and the amplitude of the tool can affect the bonding quality 22. The ball bond includes the enlarged spherical portion of the wire sometimes referred to as the nail head and formed by the flameoff and first bonding operation in thermal compression and thermosonic process,the underlying bonding surface, and the intermetallic weld interface. This chapter presents the wire bonding process, including the influence of process parameters on the wire bonds and bond process optimization. In the present study, the shear strength results of the copper ball bond show better performance than the gold bond. The characteristics of the crescent bond process with insulated au wire are investigated. Wire bonding is a solid state welding process, where two metallic materials are in intimate contact, and the rate of metallic interdiffusion is a function of temperature, force, ultrasonic power, and time.
The goal of this thesis is to improve the understanding of the stitch bonding process in microelectronic wire bonding. First, an if is applied to produce an initial deformation of the wire. The wire used in wirebonding is usually made either of gold au or aluminum al, although cu wirebonding is starting to gain a foothold in the semiconductor. Many numerical studies have been reported for gold ball bonding, wire bonding 2226, bump bonding 18,27 and tab 1,28 to quantitatively understand the plastic deformation of the wire or bump and tab leads, stress conditions during bonding, and interfacial intimate contact process between the wire and pad. Approximately 90% of all ic assembly in semiconductor packages is manufactured using gold ball bonding process, while aluminum wedge bonding is used to produce about 10% of other wire bonding requirements on printed. To better understand the bonding formation mechanism, a dynamic finite element model of the tsfc bonding process was developed, where the soften effect caused by the heat stage and ultrasonic vibration was considered in the constitutive relation of the gold bump. Small precision tools gold ball wire bonding process. The wire heated in some cases is pressed against the hot surface at 150 deg.
Depending on bonding agent heat and ultrasonic energy, the bonding process can be defined to three major processes. Experimental and modeling studies of looping process for wire. The classroom training is open to anyone, but the hands on activities are limited to 3 or 4 students at a time due to logistical reasons. At the start ofthe gold bonding process, a gold ball is melted by means ofan electrical discharge at the wire tip, iethe. A wire bond process optimization is essential for bonding process stability.
Kickup phenomenon during looping is an important factor in thermosonic wire bonding. In particular, it focuses on investigating the effect of the process parameters bonding force, scrub amplitude, and skid on experimental bond quality responses, including qualitative nonsticking, sticking, and taillifting and quantitative stitch pull force. During thermosonic bonding cher ming tan, senior member, ieee, and zhenghao gan abstract aluminum bondpad peeling was observed in a newly developed thermosonic wirebonding process for chiponboard assembly. The following is a basic procedure for wire bond process optimization. Thermosonic bonding is widely used to wire bond silicon integrated circuits into computers. Pdf multiresponse optimisation of thermosonic copper. The boards were plated with 50 microinch of nickel and 200 micro inches of type iii. Introduction of a new wire bonding process known worldwide as thermosonic bonding. Heat applied to the assembly held in the work holder to assist in the bonding process. Process advantages of thermosonic wedgewedge bonding. Small precision tools basics of ball bonding process.
Wirebonding is a solid phase welding process, where the two metallic materials wire and pad surface are brought into intimate contact. Abstract thermosonic ball bonding is a major interconnect process in microelectronics packaging and is positioned to remain one of the key process technologies available to package designers in the near future. Visual and mechanical testing methods of wire bonds. Alexander coucoulas was named father of thermosonic bonding by george harman, the worlds foremost authority on wire bonding, where he referenced coucoulass leading edge publications in his book, wire bonding in microelectronics. Looping is one of the key technologies for modern thermosonic wire bonders, and it has been affected by many interacting factors. Coucoulas, alexander father of thermosonic bonding, ultrasonic welding of aluminum leads to tantalum thin films, trans. He was named father of thermosonic bonding by george harman, the worlds foremost authority on wire bonding, where he referenced coucoulass leading edge publications in his book, wire bonding in microelectronics.
The bond type practiced was a thermosonic bond using 0. C or less at low force and vibrated for a limited period of time to achieve the bond. A process which involves the use of force, time, ultrasonics and heat to join two materials. Experimenting with these parameters is time well spent, and is an important step toward developing a robust wire bond process. Thermosonic bonding using auau process finetech bonder. However, the introduction of lowk dielectric materials, and the feature size decrease of ic chips to follow moores law, pose great integration challenge. The third main wire bonding process combines the best features of thermocompression and ultrasonic bonding. Basic wire bonding theory parameter development practical applications presented by kyle huth of k h sales. Optimization, bondability, and reliability a thesis presented to the faculty of california polytechnic state university, san luis obispo in partial fulfillment of the requirements for the degree master of science in mechanical engineering by minhnhat ba le june 2009. Effect of efo parameters on cu fab hardness and work hardening in thermosonic wire bonding. This is a good choice for lowloop, and short wire type of wire bonding.
Tab thermosonic bonding is a modification of the wellestablished technique of thermosonic wire bonding in which heat and ultrasonic energy are applied together in addition to force to produce a solidstate diffusion bond. The test result shows that the analysis on the wire. The primary focus of this thesis is to provide a better understanding of the efo process in order to expedite the introduction of novel wire materials into industry. Course outline day 1 classroom activities am session 08301200 hrs the wire bond process thermosonic gold ball bonding. Simulation of wire bonding process using explicit fem with. Wire bonding guidelinesblogjaapson blog and resource center. Thermocompression bonding an overview sciencedirect topics. Pdf microelectronic wire bonding with insulated au wire. Effect of temperature on deformation characteristics of gold. In this study, the wire looping process was observed with a highspeed camera, and the evolution of wire profiles during looping and the capillary trace were obtained through experiments. A better understanding how bond strength depends on process parameters could increase productivity by speeding up process rampup and increasing process reliability. Investigation of ultrasonic vibrations of wirebonding.
The ball bond includes the enlarged spherical portion of the wire sometimes referred to as the nail head and formed by the flameoff and first bonding operation in thermal compression and thermosonic process, the underlying bonding surface, and the intermetallic weld interface. In hybrid microcircuit technology handbook second edition, 1998. The tail breaking process has been described in and is here studied by investigating tail bond imprint micrographs as illustrated in fig. There are two wire bonding processes that are used, thermosonic ts gold ball wire bonding and ultrasonic us aluminum wedge wire bonding. Workshop wire bonding for mems technology cluster september 2012 jan eite bullema 2.
Thermosonic wire bonding process simulation and bond pad. Once the surfaces are in intimate contact, electron. Impact on the bonding strength of the ultrasonic amplitude, ultrasonic frequency and the friction between wire bond and bond pad are studied. Wire bonding process the critical steps in the wire bonding process include achieving reliable bonds first bond, second bond, and tail bonds, maintaining desired loops, and positioning the bonds accurately. Owing to the well proven reliability of thermosonic.
The wire loops are oriented perpendicular to the ultrasonic horn. Gold wire bonding induced peeling in culowk interconnects. Device attachment methods and wirebonding notes for rt. Ultrasonic welding of aluminum wires to tantalum thin film circuits 1400a deposited on glass substrates resulted in low. The goal is to teach the process of wirebonding, which includes the wire.
Wire bonding guidelines jaapson blog and resource center. A study of the electrical flame off process during. Thermosonic wedgewedge bonding using dosed tool heating. Currently, there are many flip chip techniques, such. Effect of temperature on deformation characteristics of. Thermosonic wire bonding process simulation and bond pad over active stress analysis conference paper pdf available in ieee transactions on electronics packaging manufacturing 311. Failure mechanisms of aluminum bondpad peeling during.
Thermosonic wire bonding process simulation and bond pad over active stress analysis abstract. Coucoulas, alexander, ultrasonic welding of aluminum. Gold ball bonding with 25um diameter wire was performed. Simulation of wire bonding process using explicit fem with ale remeshing technology volume 36 issue 1 c. In the wirebonding process the wire, usually made of gold or aluminum, is used to establish the electrical connection from the semiconductor. Thermosonic wire bonding process simulation and bond pad over active stress analysis. The process optimization defines a process parameter window for ball and wedge bond quality.
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