Effect of thermal aging on interfacial behaviour of copper ball bonds

Thermosonic copper ball bonding is an interconnection technology that serves as a viable and cost-saving alternative to gold ball bonding. However, the reliability of copper bonds remains to be ascertained. Intermetallic compounds (IMCs) and possible voids and cracks may grow and propagate at the interface of bonds during their service. The proper IMCs formation is beneficial to bonding strength but an excessive growth of IMCs, voids and cracks can induce a mechanical failure and increase a contact resistance. In this study, a 99.99% copper wire with diameter 50.4 mum was bonded to a Al-1%Si-0.5%Cu metallisation pad by thermosonic bonding. Scanning electron microscopy, energy dispersive X-ray spectrometry, dual focused ion bean and transmission electron microscopy (TEM) were used to investigate the interfacial evolution of such formed joints during the thermal ageing, and kinetics of Cu-Al IMCs growth was established. The results showed no IMCs at the initial bonded Cu/Al interface. To study the Cu-Al IMCs growth, the samples were thermally aged for different times at a temperature from 200 degC to 300 degC to accelerate interfacial evolution. The growth of Cu-Al IMCs followed the parabolic law as a function of aging time at a certain aging temperature, and it is more sensitive to temperature compared to time. The activation energy of Cu-Al IMC growth was obtained from the Arrhenius plot. Voids and cracks, which are commonly present in gold ball bonds due to thermal aging, were not observed in copper ball bonds even after aging at 200 degC for 2900 hours. Finally, the structure of Cu-Al IMCs was confirmed to be Cu9Al4 by selected area electron diffraction with TEM

Effects of process parameters on bondability in thermosonic copper ball bonding

Thermosonic copper ball bonding is an absorbing interconnection technology that serves as a viable and cost saving alternative to gold ball bonding. Its excellent mechanical and electrical characteristics make copper ball bonding attractive for high-speed, power devices and fine-pitch applications. However, copper is easily oxidized and harder than gold, which causes some critical process problems in connection with bondability. In this study, a 50 mum copper wire with purity of 99.99% was bonded on aluminum metallization with thickness 3 mum using an ASM angle 60 automatic thermosonic ball/wedge bonder. Experimental studies of copper free air balls (FABs) formation and bonding process were conducted to establish the bonding mechanism and to explain the effects of process parameters on bondability. A micro-slipping model was proposed to account for the effects of the ultrasonic power and bonding force on bondability. It was found that the bondability was determined by a slip area at the bonding interface. The occurrence of bonding only at the periphery of the contact area between FAB and aluminum metallization was attributed to partial slips at the bonding interface. Variation in the ultrasonic power and bonding force that lead to different stick-slip modes, can effect bondability in the ultrasonic bonding process. It is important to set a proper bonding time to achieve interatomic bonding without causing fatigue rupture of microjoints. It was also found that preheating of the chip to a certain temperature can improve bondability

TEM Microstructural Analysis of As-bonded Copper Ball Bonds on Aluminum Metallization

In this study, the nano-scale interfacial details of ultrasonic copper ball bonding to an aluminum metallization in the as-bonded states were investigated using high resolution scanning/transmission electron microscopy with energy dispersive spectroscopy. Our results showed that ultrasonic vibration swept aluminum oxide and copper oxide in some regions of contacting surface, where an approximate 20 nm Cu-Al intermetallics (i.e. CuAl2) formed. In the regions where oxide remained, aluminum oxide layer connected with copper oxides layer. No nano-level voids or gaps were observed at the central area of the interface, including the regions with oxide. Calculation of interfacial temperature showed that the ultrasonic vibration increased the flash temperature up to 465degC which was believed to improve the interdiffusion for the formation of Cu-Al intermetallics

Vektor Malaria Baru di Kabupaten Kotabaru, Provinsi Kalimantan Selatan, Indonesia

Nyamuk Anopheles merupakan vektor dari Malaria. Dari sekitar 400 spesies nyamuk Anopheles telah ditemukan 67 spesies dapat menularkan malaria dan 24 diantaranya ditemukan di Indonesia. Kabupaten Kotabaru merupakan kabupaten endemis malaria di Kalimantan Selatan. Data mengenai spesies vektor malaria spesifik pada suatu daerah sangat berperan penting sebagai salah satu bahan rekomendasi bagi tindak lanjut kebijakan pengendalian malaria. Penelitian bertujuan untuk mengetahui data vektor malaria di Kabupaten Kotabaru melalui uji PCR. Penelitian deskriptif dengan desain cross sectional. Penangkapan nyamuk dilakukan di Desa Siayuh Trans dan Magalau Hulu, tambang emas Kura-Kura dan Desa Muara Uri dengan metode penangkapan UOL, UOD, dinding dan kandang. Uji PCR dilaksanakan di laboratorium biomolekuler BBPPVRP Salatiga pada bulan Februari-April 2015. Hasil penangkapan nyamuk didapatkan 345 ekor nyamuk Anopheles yang terdiri dari 9 spesies: An. barbirostris, An. tesselatus, An. balabacensis, An. vagus, An. hyrcanus group, An. peditaeniatus, An. kochi, An. flavirostris, An. umbrosus. Seluruh nyamuk Anopheles yang didapatkan dibuat 56 pool sampel Anopheles sp untuk diuji PCR yang telah diklasifikasikan berdasarkan spesies, tanggal dan metode penangkapan. Hasil PCR terindentifikasi 3 spesies vektor malaria di Desa Siayuh Trans yaitu An. vagus, An. peditaeniatus dan An. tesselatus yang merupakan vektor malaria baru di Propinsi Kalimantan Selatan

Diagnosing the role of the state for local collective action : types of action situations and policy instruments

Unidad de excelencia María de Maeztu MdM-2015-0552This paper presents a diagnostic approach to the role and capacity of governments to facilitate local collective action and alleviate environmental problems. The paper adds to a nascent scholarship aiming to conciliate theories on "governance by government" and "governance by self-organization". We adopt two premises for that purpose: (1) policy instruments shall be tailored to the strategic nature of local resource management decisions; and (2) such nature is not static and can be modified via governmental policies. We first build on the Institutional Analysis and Development (IAD) framework to characterize the decision-making situations that local resource users face and the local rules that shape said situations. Then, based on common pool resource (CPR) and policy instrument choice theory, we identify four mechanisms through which different policy instruments can facilitate local collective action (change in payoffs and their perception, reduction of transaction costs, reduction of uncertainty, and normative consonance). This analytical approach is then applied to four illustrative cases of water management in Germany, France, Greece and Spain. As shown, local resource users are embedded in not one but many overlapping decision-making situations. In this context, the promotion of collective action is rarely accomplished via a single policy instrument or mechanism but via bundles of them. Also, the paper illustrates the importance of understanding how governmental policies modify the structure of rules and incentives that affect local resource users, potentially facilitating local collective action and the solution of environmental problems

Supplemental Material - An emerging ‘China-threat-corporatism’? CRRC’s acquisition of a German locomotive company and its impact on labour relations

Supplemental Material for An emerging ‘China threat corporatism’? CRRC’s acquisition of a German locomotive company and its impact on labour relations by Stefan Schmalz and Lea Schneidemesser and Hui Xu in European Journal of Industrial Relations.</p

God&apos;s Will and the Origin of the World. &#8216;Abd al-Latif al-Baghdadi&apos;s Sources and Arguments

As well stated by Herbert Davidson in the Introduction to his famous book Proof for Eternity, Creation and the Existence of God in Medieval Islamic and Jewish Philosophy: \u201cThe issue of eternity and creation provided an arena for determining the relationship of God to the universe, for determining, specifically, whether God is a necessary or a voluntary cause\u201d,1 whether volition is a further attribute for deity in addition to the uncaused cause, the incorporeal and the One. This paper addresses \u2bfAbd al-La\u1e6d\u12bf al-Ba\u121d\u101d\u12b's position in this arena: his sources and arguments in the Book on the Science of Metaphysics (Kit\u101b f\u12b \u2018Ilm M\u101 ba\u2018d al-\u1e6dab\u12b\u2018a)

Turing mechanism underlying a branching model for lung morphogenesis

<div><p>The mammalian lung develops through branching morphogenesis. Two primary forms of branching, which occur in order, in the lung have been identified: tip bifurcation and side branching. However, the mechanisms of lung branching morphogenesis remain to be explored. In our previous study, a biological mechanism was presented for lung branching pattern formation through a branching model. Here, we provide a mathematical mechanism underlying the branching patterns. By decoupling the branching model, we demonstrated the existence of Turing instability. We performed Turing instability analysis to reveal the mathematical mechanism of the branching patterns. Our simulation results show that the Turing patterns underlying the branching patterns are spot patterns that exhibit high local morphogen concentration. The high local morphogen concentration induces the growth of branching. Furthermore, we found that the sparse spot patterns underlie the tip bifurcation patterns, while the dense spot patterns underlies the side branching patterns. The dispersion relation analysis shows that the Turing wavelength affects the branching structure. As the wavelength decreases, the spot patterns change from sparse to dense, the rate of tip bifurcation decreases and side branching eventually occurs instead. In the process of transformation, there may exists hybrid branching that mixes tip bifurcation and side branching. Since experimental studies have reported that branching mode switching from side branching to tip bifurcation in the lung is under genetic control, our simulation results suggest that genes control the switch of the branching mode by regulating the Turing wavelength. Our results provide a novel insight into and understanding of the formation of branching patterns in the lung and other biological systems.</p></div