The multiple responses are transformed into a synthetic index prior to optimization. Thermosonic wire bonding is one of the methods that can provide this interconnection using fine wires which are bonded first on to metallized pads of the ic and then to the substrate terminals. The impact of capillary profile and bonding process parameters which include ball diameter, bonding temperature and bond wire material properties are studied to optimize the wire bonding assembly process. Evaluation of wire bonding performance, process conditions. Wire bonding capillary profile and bonding process parameter optimization simulation. When wire bonding on multilayer substrates, wirebond pads should be a minimum of 10 mm from the edge of adjacent conductors to allow for registration, printing, and wire bonding tolerances. However, the high price of au has been pushing the wire bonding industry to look for alternative bonding wire materials. Wire bonding is a process that is usually associated with chip bonding to hard substrate, although recent publications shown good results while bonding to soft substrates if the right bonding parameters are employed 3. Given the cost and performance advantages associated with cu wire, it is being increasingly seen as a candidate to replace au wire for making interconnections in. On the left is a list of several problems affecting wire bonds.
Wire bonds can be either ballwedge bonds or wedgewedge bonds. For gold wire, heat is added to increase interatomic diffusion and accelerate bond formation. Inderjit singh, shin low, syu fu song, chen shih jung, lin ming san, ivy qin, cuong huynh, horst clauberg, son truong nguyen, bob chylak, hui xu, and viola l. However, the replacement of gold wire with copper wire introduces hardness related issues as copper is much harder than gold. Wire bonding is an electrical interconnection technique using thin wire and a combination of heat, pressure andor ultrasonic energy. Hesse mechatronics wire bonding technology university. Fine pitch cu wire bonding capability process optimization. Selecting the wire the choice of wire diameter depends on the wire bond pitch, current carrying capacity, and cost. This is an accepted version of a paper published in. Wire bonding is a solid phase welding process, where the two metallic materials wire and pad surface are brought into intimate contact. Tis journey to highvolume copper wire bonding production. 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. The process optimization defines a process parameter window for ball and wedge bond quality.
Reduction of ultrasonic pad stress and aluminum splash in. Bonding parameters such as ultrasonic power, ultrasonic generator current, electric flameoff current, firing time, bonding force, and temperature are discussed. Leading wire bonding applications the most advanced wire bonding applications include. We examine significant factors affect the finepitch cu wire bonding process. In summary, the development on various wire bond technologies with insulated wire has widen the application of insulated wire.
A wire bond process optimization is essential for bonding process stability. The industry is moving towards using cu, but there are many companies still unprepared to implement cu wire bonding because of the cost. The wire bonding process involves two items, namely, the wire bonder and the bonding wire i. A cu ball bonding process is optimized with reduced pad stress and splash, using a 25.
The bond force initially deforms the wire and couples the ultrasonic energy into the wire and scrubs the wire into the pad. To obtain the best wire bonding quality, we employed taguchi methods in optimizing the cu wire bonding process. Wirebonding pressure temperature ultrasonic energy wire pad. Experimenting with these parameters is time well spent, and is an important step toward developing a robust wire bond process. The use of a crossbonding tool can help reduce the extent of ultrasonic cupping problems. The principle difference between the two processes is that the aluminum wire is bonded in an ultrasonic bonding process at room temperature, whereas gold wire wedge bonding is performed through a. A combined approach, encompassing upgraded wire bonders and specially designed bonding tools and bonding wire, provides a unique opportunity to develop integrated solutions to these technical challenges. The impact of capillary profile and bonding process parameters which include ball diameter, bonding temperature and bond wire material properties are studied to optimize the wire bonding assembly. Proper optimization and process window development for wire bonding is essential to minimize nonstick on pad, lifted or broken wire bonds. Parameters optimization of copper wire bonding on thin small. This technique provides more control over loop height and bond placement. Wire bonding in microelectronics, third edition, has been thoroughly revised to help you meet the challenges of todays smallscale and finepitch microelectronics. Depending on bonding agent heat and ultrasonic energy, the bonding process can be defined to three major processes. Intelligent production of wire bonds using multiobjective.
Copper wire bonding has obtained prevalent owning to its economic advantage and superior electrical property. These stresses are due to the mismatch of ctes ofmetal wire and bond pads and substrate materials, and residual stress fromthe bonding process. 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. Cu wire bonding has taken over au wire bonding due to its cost savings and other performance advantages such as higher mechanical strength for. A greyfuzzy taguchi method is proposed to optimize the finepitch cu wire bonding. Then you can start reading kindle books on your smartphone, tablet, or computer no kindle device required. Development of a fast method for optimization of au ball. Optimizing a wire bond process begins with a clear understanding of the bonding equipment, machine setup, the response. Gold wire provides the ability to use a ball and stitch process.
Optimization of the cu wire bonding process for ic. 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. A multidisciplined team is able to drive the optimization process farther and faster than groups that only focus on smaller areas of the process. Define ball and wedge bond specifications to be use as target response in optimizing a given application. Development of a fast method for optimization of au ball bond. This chapter presents the wire bonding process, including the influence of process parameters on the wire bonds and bond process optimization.
Wirebonding is a process that is usually associated with chip bonding to hard substrate, although recent publications shown good results while bonding to soft substrates if the right bonding parameters are employed 3. Copper cu 26 silver ag 7, and alloyed wires 8 have emerged as potential replacement to au in recent years. The experiments were focused on cu free air ball fab formation and ball bonding process. Nasa electronic parts and packaging nepp program website.
Acoff 2012 pdcoated cu wire bonding reliability requirement for device design, process optimization and testing. This paper reveals wire bonding parameters optimization in order to implement cu wire bonding in high volume production environment with good bondability and bond reliability. The results help in cost saving and yield improvement for the subject company. Wire bond process starts by melting the end of the wire hold by a bonding tool known as. The setup of a wire bonding process can be tedious and dependent on the skill of the process engineer. Parameters optimization of copper wire bonding on thin.
Optimizing the finepitch copper wire bonding process with. The following is a basic procedure for wire bond process optimization. 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. Thermosonic gold bonding includes heat treatment and can be used to form solidstate bonds below the melting point of the mating metals for ballwedgebonding, a gold ball is formed before the bonding process by melting the end of the wire applying a high voltage devices and packaging power electronic modules. Process optimization and reliability study for cu wire bonding. Wire bonding process optimization is normally performed through design of experiment doe to further understand how changes affect the outputs.
In this paper, a methodology for wire bonding parameter modeling is developed, which considers the capillary, fab and device on silicon. The parameters of interest were electronic flameoff efo gap, flow rate of. Wedge bonding technique can be used for both aluminum wire and gold wire bonding applications. 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. Pdf process optimization approach in fine pitch cu wire bonding. Wirebonding process begins by firmly attaching the backside of a chip to a.
Introduction wirebonding is the most common interconnect technology in semiconductor assembly providing electrical connection between silicon chip and the external leads using fine bonding wires. This article reports investigations of the process optimization of ball bonding for 1. The use of a cross bonding tool can help reduce the extent of ultrasonic cupping problems. Genetic algorithms gas are optimization techniques based on the concepts of. The process characterization of insulated auflash pdcu for.
Small precision tools wire bonding process optimization. Once the surfaces are in intimate contact, electron sharing or interdiffusion of atoms takes place, resulting in the formation of a bond. Optimization of the cu wire bonding process for ic assembly. A study on the effect of bond stress and process temperature. Using design of experiments to optimize wire bond processes. Once the surfaces are in intimate contact, electron sharing or interdiffusion of atoms takes place, resulting in the formation of wirebond. The technician needs to prepare and sets the capillary and the. During the bonding process, power, time, and force interact to reduce the impact of forces acting on the material and wastage on bonding capillaries.
Pdf wire bonding capillary profile and bonding process. Silver wire bonding sep 30, 20 page 2 of 3 process control controlling pad structure damage of ultrafine pitch cu bonding key controls were put in to work on the following, free ball oxidation by forming balls in an oxygen free environment in all our bonder types. Copper wire bonding book lays out the challenges involved in replacing gold with copper as a wire bond material, and includes the bonding process changesbond force, electric flame off, current and ultrasonic energy optimization, and bonding tools and equipment changes for first and second bond formation. The wire bonder is provided by the equipment supplier. In the modified process, an insulation layer removing stage cl eaning stage is inserted befo re the bonding stage. The nordic electronics packaging guideline chapter a. Wire bonding process is the key driver of the package assembly yields. More than 90% of the chip interconnections produced annually. Optimizing the ic wire bonding process using a neural networks. The vast majority of ics are interconnected using the wire bonding process 2. Pdf wire bonding capillary profile and bonding process parameter. Prepping the copper wire bonding process required several years of preliminary studies and experiments, extensive testing and process qualification that customers can have confidence in today figure 3. Surface cleanliness and bond pad metallurgy are critical for successful wire bonds.
Pdcoated cu wire bonding reliability requirement for. Request pdf fine pitch cu wire bonding capability process optimization and reliability study wire bonding has been around for over 70 years and it is still growing. Doe is normally conducted for any new devices, new capillary design or changes made to the wire or substrate, whereby a new process window need to be defined. Typical wire bond process optimization small precision tools.
Bonding process optimization and characterization cyril buttay, amandine masson, jianfeng li, mark johnson, mihai lazar, christophe raynaud, herve morel to cite this version. A prototype of a multiobjective optimizing bonding machine mobm is presented. Two examples of recent efforts in wire bonding are 1 bonding on novel lowk vlsi layer systems with low mechanical robustness and b using cu wire bonds on cu or al pads. The industry standard guide to wire bonding fully updated the definitive resource on the critical process of connecting semiconductors with their packages.
Pdf with sio 2 dielectric under aluminum pads, a 60 m bond pad pitch with 52 um bond pad opening cu wire bonding process was. Assembly process optimization wire bond process optimization begins with a clear understanding of the bonding equipment, machine set up, the response variables involved and their relationship to one another. With cu wire bonding technology, the production yield increased from 98. With each new wire material, the bonding process is. These advanced applications often require more process optimization. Peter majewicz, program manager jonathan pellish, deputy manager.
Introduction optoelectronic packages are classic hybrids with some new optomechanical variations. The two main wire bonding process technologies are ultrasonic wedgewedge. Enter your mobile number or email address below and well send you a link to download the free kindle app. Failure modes in wire bonded and flip chip packages. The process optimization of the first ball bonding for. A common strategy to address such bonding challenges is to carry out. The impact of capillary profile and bonding process parameters which include ball diameter, bonding temperature and bond wire material properties are studied to. Rutherford prepared by sandia national laboratories albuquerque, new mexico 87185 and livermore, california 94550 sandia national laboratories is a multiprogram laboratory managed and operated by sandia corporation. The used wire bonding techniques and materials are discussed, and the. Process quality improvement in thermosonic wire bonding. Structure optimization of au wire wedgebond for high. This paper presents a physical model of the ultrasonic wire bonding process including the friction contact between tool and wire.
This thesis presents a systematic study of the effects of 120 khz ultrasonic frequency on the reliability of fine pitch gold wire bonding. The process optimization of the first ball bonding for copper. Levine, how to optimize and control the wire bonding process. The proper bond pad cleanliness also contributes to reliable wire bonds. Cd includes all of the books fullcolor figures plus animations. Design of experiments approach for improving wire bonding quality.
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