Thesis (Ph. D.)--University of Texas at Austin, 2004. / Supervisor: John G. Ekerdt. Vita. Includes bibliographical references.

Not available / text

Wire bonding has been used in integrated circuit packaging for many decades because of its high reliability and performance. The most common metal used has been gold, but with the surge in commodity prices of gold in recent years, copper wire is now used to altered gold wire for cost saving. Many challenges have to be solved to meet its application requirement; coating is one of the applications. In this study, a 3D coated copper wire and coated Al pad is built by finite element method to simulate ultrasonic bonding and thermosonic bonding. To consider the effect of coated material to stress and strain field on ultrasonic bonding and the effect of coated material to temperature field on thermosonic bonding. Then use the Taguchi experiment method to discuss the effect on Cu-Ball and Al pad under different coated material and thickness combination. The results show that with coated material on Al pad or copper wire could reduce more than 48% of effective plastic strain after the bonding process, it obviously reduce the Al splash phenomenon in copper wire bonding. But the coated material such like palladium and nickel which have lower thermal conductivity would resist the heat transfer. And the Taguchi experiment method shows that the most effective way to reduce the effective stress during impact stage and ultrasonic vibration stage is to increase the thickness of palladium and nickel respectively, and when the thickness of coated material Au reached 0.01£gm could increase the temperature of Cu-Ball and Al pad mostly.

Ball bonding with gold wire has been the preferred choice to connect semiconductor chip and a lead frame. Recently, copper wires have been increasingly used to replace gold wires because of the rising price of gold. However, copper is harder than gold and has the tendency to induce the damage of bond pad or other underlying layers. Herein, Al pad material has to be changed from bulk to single crystal with (100) surface orientation in order to improve bonding reliability. Firstly, finite element method was adopted to simulate 3D wire bonding. Also, from the impact of gold wire bonding, the stress concentration was found on pad and underlying layers due to the higher elastic modulus of bulk Al. During copper ball impact, there is not only the serious stress concentration at pad, but also a pad splash due to the insufficient strength of bulk Al, even though bulk Al has a lower elastic modulus. Secondly, material properties of Al(100) were obtained by uniaxial tensile tests at constant speed. With molecular dynamics method, the incorporated result showed that Al(100) has the lower elastic modulus and higher yield strength than those of bulk material. Finally, single crystal Al(100) was used, instead of bulk material, to carry out copper ball impact process by using multi-scale simulation. Al(100) material is able to transform impact energy into the resilience of strain energy effectively owing to its high yield stress and low elastic modulus. Results show that the application of Al(100) material reduces the effects of stress concentration and pad ¡§splashing¡¨ successfully during copper ball impact process.

Submitted by Silvana Teresinha Dornelles Studzinski (sstudzinski) on 2016-08-04T14:39:04Z No. of bitstreams: 1 João Pedro Gonçalves Trevizan_.pdf: 2398963 bytes, checksum: 7bbf859367acdb155c3b917d8275c41d (MD5) / Made available in DSpace on 2016-08-04T14:39:04Z (GMT). No. of bitstreams: 1 João Pedro Gonçalves Trevizan_.pdf: 2398963 bytes, checksum: 7bbf859367acdb155c3b917d8275c41d (MD5) Previous issue date: 2016-06-15 / itt Chip - Instituto Tecnológico de Semicondutores da Unisinos / PADIS - Programa Federal de Apoio a Indústria de Semicondutores / Este estudo avalia uma proposta de substituição de fio de ouro por fio de cobre no processo de wire bonding em memórias DRAM DDR3 encapsuladas no Brasil. A viabilidade técnica da aplicação desta tecnologia para este componente foi testada na prática em uma empresa coreana, com a produção de amostras e verificação das características de qualidade das mesmas. Após otimização de parametros da primeira solda por DOE, foi possível obter resultados dentro das especificações do processo e semelhantes aos obtidos com o fio de ouro. Após a confirmação da viabilidade técnica, foi verificado a viabilidade econômica deste projeto, calculando o custo de implementação e estimando o tempo para retorno do investimento através dos métodos de payback simples e descontado. Devido à necessidade de aquisição de máquinas soldadoras de custo elevado, o payback descontado resultou em seis anos e onze meses, o que representa um risco alto considerando o dinamismo do mercado de semicondutores e a eminente substituição do encapsulamento BOC pela tecnologia de flip chip / This study evaluates the proposal of gold wire for copper wire replacement in the wire bonding process used in DRAM DDR3 memory packaging in Brazil. The technical feasibility of applying this technology to the component has been verifyed in practice on a Korean company, with the production of samples and the examination of quality characteristics, such as bond pull force and bond shear strenght, intermetallic compound and bonding pad structure. After parameters optimization of the first bond by DOE, it was possible to obtain results within process specifications and similar to those obtained with the gold wire. After confirming the technical feasibility, the economic viability of this project was verified by calculating the cost of implementation and the necessary time to recover the investment, through the simple and discounted payback methods. Because of the need of purchasing costly wire bonding machines, the discounted payback resulted in six years and eleven months, which represents a high risk investment, considering the semiconductor market dynamism and the imminent replacement of BOC package by flip chip technology.

With the reliability requirements of automobile microelectronics pushing towards near 0 ppb levels of failure control, halide induced corrosion issues in wire bonded devices have to be tightly controlled to achieve such a high reliability goal. With real-time corrosion monitoring, for the first time we demonstrated that the explosive H2 evolution coupled with the oxygen reduction reaction, occurring at the critical Al/Cu interfaces, is the key driving force for the observed aggressive corrosion. Several types of passivation coating on Cu wire surfaces to effectively block the cathodic H2 evolution were explored with an aim to disrupt this explosive corrosion cycle. The properties of the protective coating were evaluated using various analytical techniques. The surface coating exhibited high thermal stability up to 260 °C (evaluated using TGA analysis). A uniform, highly hydrophobic coating (surface contact angle of >130° with water), was achieved by carefully controlling CVD parameters such as time of deposition, surface control of Cu metal, amount of inhibitor compound loading, temperature of coating process etc. FTIR spectroscopy combined with corrosion screening was used to optimize the CVD passivated coating with strong chemisorption. SEM and EDX, XPS were carried out on various coated surfaces to understand the composition and selectivity of the film formed through this surface treatment. The surface selective nature of this coating (towards Cu) proved helpful in preventing potential delamination issues during epoxy molding process. The corrosion testing was carried out via HAST testing at 130°C, 2 atm pressure and 100% RH for 48 hours. Delamination analysis and continuity test showed that the inhibitor compound was able to effectively prevent the corrosion even after exposure to harsh HAST conditions.

Thermosonic ball bonding is the most popular method used to create electrical interconnects between integrated circuits (ICs) and substrates in the microelectronics industry. Traditionally gold (Au) wire is used, however with industry demands for lower costs and higher performance, novel wire materials are being considered. Some of these wire materials include Cu, insulated, and coated wires. The most promising of which being Cu wire. Some of the main issues with these wire materials is their performance in the electrical flame off (EFO) step of the wire bonding process. In the EFO step a ball called the free air ball (FAB) is formed on the end of the wire. The quality of the FAB is essential for reliable and strong ball bonds. In Cu wire bonding the hardness of the FAB and oxidation are the main issues. A hard FAB requires larger bonding forces and US levels to make the bond which increases the likelihood of damage to the IC. Excessive oxidation acts as a contaminant at the bond interface and can also influence the shape of the FAB. Shielding gases are required to reduce oxidation and improve FAB quality. This thesis focuses on the EFO process and the influence of EFO parameters and shielding gases on Au and Cu FABs. 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. Several different experiments are performed on an automated thermosonic wire bonder with 25 µm Au and Cu wires to investigate the EFO process during ball bonding. The effects of EFO parameters on the hardness and work hardening of FABs and the effects of shielding gas type and flow rates on the quality of the FABs are determined. The EFO discharge characteristics in different shielding gases is also studied to better understand how the composition of the atmosphere the FAB is formed in influences the energy input via the EFO electrical discharge. Using the online deformability method and Vickers microhardness testing it is found that the EFO current (IEFO) and EFO time (tEFO) have a large influence on the hardness and work hardening of Au and Cu FABs. A harder FAB produced with a large IEFO and low tEFO will work harden less during deformation. The bonded ball will be softer than that of a FAB produced with a lower IEFO and higher tEFO. The online deformability method is found to be twice as precise as the Vickers microhardness test. An online method for characterizing the quality of FABs is developed and used to identify shielding gas flow rates that produce defective FABs. The EFO process for an Au wire and two Cu wire materials is investigated in flow rates of 0.2-1.0 l/min of forming gas (5 % H2 + 95 % N2) and N2 gas. All three of the most common FAB defects are identified with this online method. It is found that good quality FABs cannot be produced above flow rates of 0.7 l/min and that H2 in the shielding gas adds a thermal component to the EFO process. It is recommended that the gas flow rate be optimized for each new wire type used. The EFO discharge power is measured to be 12 % higher in a N2 gas atmosphere than in a forming gas atmosphere. The lower ionization potential of the forming gas leads to a higher degree of ionization and therefore lower resistance across the discharge gap. It was found that the discharge power does not determine the energy transferred to the wire anode because the Au FAB produced in forming gas has a 6 % larger diameter than that of the FABs produced in N2 gas. Other factors that effect the voltage of the EFO discharge include the controlled EFO current, the discharge gap, and the wire anode material.

Thermosonic ball bonding is the most popular method used to create electrical interconnects between integrated circuits (ICs) and substrates in the microelectronics industry. Traditionally gold (Au) wire is used, however with industry demands for lower costs and higher performance, novel wire materials are being considered. Some of these wire materials include Cu, insulated, and coated wires. The most promising of which being Cu wire. Some of the main issues with these wire materials is their performance in the electrical flame off (EFO) step of the wire bonding process. In the EFO step a ball called the free air ball (FAB) is formed on the end of the wire. The quality of the FAB is essential for reliable and strong ball bonds. In Cu wire bonding the hardness of the FAB and oxidation are the main issues. A hard FAB requires larger bonding forces and US levels to make the bond which increases the likelihood of damage to the IC. Excessive oxidation acts as a contaminant at the bond interface and can also influence the shape of the FAB. Shielding gases are required to reduce oxidation and improve FAB quality. This thesis focuses on the EFO process and the influence of EFO parameters and shielding gases on Au and Cu FABs. 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. Several different experiments are performed on an automated thermosonic wire bonder with 25 µm Au and Cu wires to investigate the EFO process during ball bonding. The effects of EFO parameters on the hardness and work hardening of FABs and the effects of shielding gas type and flow rates on the quality of the FABs are determined. The EFO discharge characteristics in different shielding gases is also studied to better understand how the composition of the atmosphere the FAB is formed in influences the energy input via the EFO electrical discharge. Using the online deformability method and Vickers microhardness testing it is found that the EFO current (IEFO) and EFO time (tEFO) have a large influence on the hardness and work hardening of Au and Cu FABs. A harder FAB produced with a large IEFO and low tEFO will work harden less during deformation. The bonded ball will be softer than that of a FAB produced with a lower IEFO and higher tEFO. The online deformability method is found to be twice as precise as the Vickers microhardness test. An online method for characterizing the quality of FABs is developed and used to identify shielding gas flow rates that produce defective FABs. The EFO process for an Au wire and two Cu wire materials is investigated in flow rates of 0.2-1.0 l/min of forming gas (5 % H2 + 95 % N2) and N2 gas. All three of the most common FAB defects are identified with this online method. It is found that good quality FABs cannot be produced above flow rates of 0.7 l/min and that H2 in the shielding gas adds a thermal component to the EFO process. It is recommended that the gas flow rate be optimized for each new wire type used. The EFO discharge power is measured to be 12 % higher in a N2 gas atmosphere than in a forming gas atmosphere. The lower ionization potential of the forming gas leads to a higher degree of ionization and therefore lower resistance across the discharge gap. It was found that the discharge power does not determine the energy transferred to the wire anode because the Au FAB produced in forming gas has a 6 % larger diameter than that of the FABs produced in N2 gas. Other factors that effect the voltage of the EFO discharge include the controlled EFO current, the discharge gap, and the wire anode material.

Made available in DSpace on 2016-12-08T17:19:36Z (GMT). No. of bitstreams: 1 Capa.pdf: 25477 bytes, checksum: 6c28599cf86569155d0b0fba73768762 (MD5) Previous issue date: 2010-07-26 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The application of the electrolytic copper rectangular wire to manufacturing of components of electric transformers and generators windings, the dimensions and mechanicals properties are factors of great importance and should be conferred and be assured during the manufacture process. The objective of this work consists of evaluating the influence of the variation of mechanical properties of the raw-material used to manufacture of rectangular wires. The study it was developed with materials of different values of hardness and variation of temperature in the lamination process, to the evaluation of the influences of this properties in the deformation of material. The revision of the chosen bibliography, presents the concepts of manufactures of lamination, strain hardening and annealing of copper, beyond referring information of the copper material, as chemical composition, electrical and mechanicals properties and etc. The methodology presents the lamination of copper material, with known dimensions and different values of hardness of raw-material, to determinate reductions of thickness of material, and was evaluated the behavior of material during the deformation, calculating the parameter of anisotropy (R). . The material processed was evaluated with relation the mechanical behavior (tractive assay) and dimension. After the accomplishment of the experiments and the evaluation of the results, a significant influence of the hardness of the substance can be verified cousin on the behavior of the deformation of the material in the lamination / Para a utilização do fio retangular de cobre eletrolítico na fabricação de componentes de enrolamentos de geradores e transformadores, as dimensões e as propriedades mecânicas são fatores de extrema importância e devem ser conferidas e asseguradas durante o processo de fabricação. O objetivo do trabalho consiste em avaliar a influência da variação das propriedades mecânicas da matéria prima e de processo empregados na fabricação dos fios retangulares. O estudo foi desenvolvido com materiais de diferentes níveis de dureza e variação dos valores de temperatura do processo de laminação, para a avaliação da influência destas propriedades na deformação do material. A revisão bibliográfica apresenta os conceitos dos processos de manufatura de laminação, encruamento e recozimento do cobre, além de informações referentes ao material, como composição química, propriedades elétricas e mecânicas. A metodologia apresenta a laminação do cobre, com dimensões conhecidas, diferentes níveis de dureza e variação da temperatura do processo, sendo realizadas reduções determinadas de espessura e avaliado a deformação do material com o cálculo do parâmetro de anisotropia (R). Tanto para a matéria prima quanto para o material laminado, as características mecânicas e dimensionais, foram avaliadas. Após a realização dos experimentos e a avaliação dos resultados, pode-se verificar uma influência significativa da dureza da matéria prima sobre o comportamento da deformação do material na laminação.

The threat posed by non-ferrous metal theft to industries in South Africa is substantial but is also regarded with indifference. A reason for this view may be that the criminal act is ordinarily not accompanied by violence and the target of the crime is an object that is far removed from the vicinity of the majority of South Africans. Non-ferrous metal theft may sometimes even be erroneously termed a victimless crime. This study endeavours to shed light on the complexities of non-ferrous metal theft and the industrial dangers that may be suffered if this crime is not eradicated. A case study from the mining industry was used to examine the nature and extent of non-ferrous metal theft. A mixed methods approach was followed in terms of which qualitative and quantitative research was done sequentially to provide the best possible representation of the situation. The participant allowed access to data over a six-year period as well as access to mine employees for interviews to assist with understanding the safety and security measures that the mine put in place to protect its workforce. This information led to another realisation, namely that if non-ferrous metal thieves cut an electricity supply line that is critical for life support and transportation in the mine, mineworkers may succumb to the harsh conditions underground. It also became evident that the police and the criminal justice system must develop a better understanding of the seriousness of non-ferrous metal theft. If this does not happen in the near future, managing the consequences of nonferrous metal theft at South African mines will become a mammoth task. Such mines and other industries affected by non-ferrous metal related theft must collaborate with each other and the police in order to understand the nature of the crime and to ensure that the prosecution of the perpetrators is handled properly. These industries should also subscribe to a pragmatic approach to crime prevention whereby various components from different crime prevention strategies are used to address the issues being experienced and whereby a unique crime prevention model for each industry and mining site can be developed. / Police Practice / M.A. (Policing)