Microelectronics applications have grown rapidly since the 1970s, and most of this growth is due to improvements in the manufacturing of chips. Once all fabrication and tests are completed, chips are separated from the wafer and assembled into the final IC package. The assembly and packaging process takes good electrical devices, places them in a package, and interconnects the device bonding pads to the package leads. Packaging provides a means of protecting the chip and attaching it into a higher level of assembly. The package serves to integrate all of the components required for a system application in a manner that minimizes size, cost, mass and complexity. Driven by growing demand for smaller, faster and cheaper electronic devices, such as PC, iPhone and internet, the semiconductor industry continues to appeal packaging technology to higher and higher levels. The proportion of world''s packaging & testing industry in the output value of global semiconductor industry climbed to 18.1% in 2009 from 17.5% in 2004, and it can promisingly reach 19.5% by 2013.

Electronic packaging technology has diversified explosively since the first ICs were produced, providing evolutionary and sometimes revolutionary advantages with each new development. Wire bonding will remain one chip and packaging interconnection technology in the foreseeable future. Thermosonic bonding utilizes a combination of heat, pressure, and ultrasonic vibration to form a metallurgical bond between two materials. The four key machine settings are: bonding work stage temperature, ultrasonic transducer power, bonding tool pressure, and bonding time. When all process variables are under control, ultrasonic and thermosonic wire bonding can be a highly reliable manufacturing process.

To meet the demands of future microelectronic mass production requirements from all different tasks, wire bonding has to achieve more improvements. In order to fulfill technological demands, modern bonding equipment improvements address the following topics:

understanding mechanism in bonding.

increasing bonding reliability.

wire looping.

flip chip technology.

integration of equipments and tools.

Progress of Advanced Packaging in Microelectronics Manufacturing[BW)] Optimizing a wire bond process begins with a clear understanding of bonding mechanism,the machine set-up, the response variables involved, and their relationship to one another. Experimenting with these parameters would be time consuming, but an important step toward developing a robust bond process. The results were obtained on our lab test-benches, which may provide some insights into a real process. It would be helpful for understanding of real industrial packaging equipments.

The technology that is used to make IC packages today has evolved largely through empirical methods. Yet in parallel with the rapid pace of the industry, a strong effort has been proceeding to develop a solid, physically based understanding of the technologies used in packaging. Our research covers a rather wide spectrum, from general principles, experimental methods, and simulation. The driving current is monitored by using a digital scope, and the vibrating targets are measured by using a Laser Doppler Vibrometer or high speed video camera. These powerful instruments are firstly used to make non-contact vibration measurements. Various analysis, including finite element simulation, wavelet analysis, serious image analysis, pattern recognition are utilized to used to find out details and differences. For assessing wire bond quality, the bonds are sheared individually, and the bond lift-off microstructures are observed by a scanning electron microscope or high-resolution transmission electron microscopy (HRTEM). Different topics, such as gold/aluminum/copper wire bond, flip-chip, stack-die, and micro-solder balls, are within our area of interests.

Just like many other physical processes controlled or driven by atomic-scale phenomena, bonding cannot be precisely described by continuum models and thus require atomic resolution in some regions of material. While dislocations clearly play a key role in the bonding process, the studies infer the role of dislocations rather than giving direct evidence of dislocation assisted strength formation. Greater insight into the phenomena that occur at bonding interfaces after ultrasonic and thermosonic bonding comes from studies that use electron microscopy to examine the microstructures of the interface of wire and substrate. The most plausible theory of the bonding mechanism seems to be that ultrasound creates and moves dislocations at the interface between two metals (or the same metals), allowing specifically enhanced diffusion. Within a few milliseconds, a bond is formed by applying an ultrasonic energy and compressive force at appropriate temperature. However there have been not sufficient studies about phases formation between dissimilar metals or how the same metals intermix during ultrasonic and thermosonic bonding. It also be expected that ultrasonic power affects dislocation density at various bonding temperatures and times and it would be interesting to systematically map out such behavior. Close studies for the interface cross-section show grain growth and crystallization, deformation substructures,slip bands and the intermetallic phases of metals in bond microstructures. We need to piece all observations together, and then find possible reason by intuition. Theses phenomenon attracted considerable interests of material scientists, experimental physicists and packaging engineers.

Lei Han, Junhui Li, and Fuliang Wang are mechanical engineering professors at Central South University, China. The authors’ group, established 2003 under the support from the China Department of Science & Technology Program 973 (Contract No.: 2003CB716202, 2009CB724203), and carried out applications in close collaboration with industrial teams. We would like to thank Prof. Jianbin Luo (Project Principal Investigator), Prof. Jue Zhong (academician of the Chinese Academy of Engineering) for their kindly help and passionate encouragement.

Here we select some of our papers accepted in international journals. The subject matter covers wire bonding, flip-chip bonding, printed circuit boards, characteristics observation of bonding interface, 3D packaging and others. It may be regarded as a profile of what we get on an ongoing journey of ours.

Frankly speaking, it is still not the ideal time to sum-up all on these fascinating areas of development for the work at hand. It is also impossible, for a group, to provide comprehensive solutions of established micro-electric manufacturing techniques and addresses all concerns of practicing engineers. We hope they will contribute to scientific community and industry as well.

We acknowledge the many wonderful graduate students who have helped to do experiments, data analysis and numerical simulation, and write down the original reports which were lately used in this book. They are: Luhua Deng, Rongzhi Gao, Hu He, Linggang Liu, Bangke Ma, Ruishan Wang, Kang Xiang, Wenhu Xu, Xiaolong Zhang. We particularly acknowledge Dr. Zhili Long, a first-rate member of our team (now at the Shenzhen Graduate School of Harbin Institute of Technology), and Prof. A. S. Voloshin (Lehigh University, USA), Igor Emri (University of Ljubljana, Slovenia), Jue Zhong (Central South University), Han-xiong Li (City University of Hong Kong), Ji-an Duan (Central South University), Yunxin Wu (Central South University) for their sincere help and valuable discussion in the early phase of the studies. Finally, we greatly appreciate the time and effort given by reviewers in evaluating papers for publication.