Person:
Wong, C. P.

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Author: Wong, C. P. × Author: Wu, Jiali × End date: 2003 × Start date: 2002 ×

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Now showing 1 - 3 of 3
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    Improved Stability of Contact Resistance of Low Melting Point Alloy Incorporated Isotropically Conductive Adhesives
    (Georgia Institute of Technology, 2003-06) Wong, C. P. ; Moon, Kyoung-Sik ; Wu, Jiali
    With the driving force of “green” revolution in the electronics industry, tremendous efforts have been made in pursuing lead-free alternatives. Although lately lead-free alloys have drawn a lot of attention, their technical weaknesses, such as high processing temperature, poor wetting and high surface tension, limit their applications on the thermally sensitive, flexible, nonsolderable substrates and the ultra-fine pitch size flip chip interconnection. Conventional isotropically conductive adhesives (ICAs) have been used widely in surface mount and die-attach technologies for electrical interconnection and heat dissipation. The low temperature processing of ICAs is one of the major advantages over lead-free solders, which brings a low system stress, simple manufacture process and the like. In order to enhance the contact resistance of ICAs, the low melting point alloy (LMA) incorporating technology has been developed by our group. In this paper, LMA fusing methods were studied, since nonfused LMA in ICAs after a curing process can adversely affect the physical property and contact resistance stability. A differential scanning calorimeter (DSC) was used for the basic examination of depleting rate of LMAs in the typical ICAs. The cross-sectional morphology, LMA distribution and intermetallic compound were investigated by a scanning electron microscope (SEM). In addition, contact resistance for the ICA formulation incorporated with LMAs under elevated temperature and humidity was evaluated.
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    Development of High Performance Interfill Materials for System Chips Technology
    (Georgia Institute of Technology, 2002-06) Wong, C. P. ; Wu, Jiali ; Bhattacharya, Swapan ; Lloyd, Courtney ; Pogge, H. Bernhard ; Tummala, Rao R.
    An innovative precisely interconnected chip (PIC) technology is currently under development at IBM to seek more effective means of creating system chips. The objective of this research is developing fabrication methods to permit the realization of high yielding large area chips, as well as chips that may contain very diverse technologies. This paper reports the use of a high-performance interfill material based on epoxy resin, which is used to connect the different chip sector macros that make up the system chip. This novel interfill material remains thermally stable through the subsequent processing temperature hierarchies during the interchip interconnection fabrication. Spherical SiO2 powders are incorporated into the epoxy resin to improve its mechanical properties, reduce coefficient of thermal expansion, and increase thermal conductivity. Adhesion and rheology of the formulated interfill materials are evaluated. Microstructure of SiO2 filled epoxy system is also investigated to confirm the reliability of the composite before and after thermal aging. Initial results indicate that the formulated EPOXY A resin composite is qualified for the system chip manufacturing process in terms of the dispensing processability, structural and mechanical integrity, and reliability.
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    Development of New Low Stress Epoxies for MEMS Device Encapsulation
    (Georgia Institute of Technology, 2002-06) Wong, C. P. ; Wu, Jiali
    In this study, a series of new low stress epoxies was introduced as conformal encapsulants, which show a high promise to meet all the requirements for the protection of the pressure sensor system. Mechanical properties such as initial Young’s modulus, toughness and ultimate tensile stress were evaluated. The more critical issue of material’s contamination resistance to the jet fuel was improved. And the mechanism behind materials lowstress and toughness behaviors was investigated from the viewpoint of microstructure.