Showing papers by "Guo-Jun Qi published in 2004"
TL;DR: In this paper, the solid state reaction between electroless Ni-P and two types of Sn-based solders (sn-3.5Ag and Sn-37Pb) has been investigated.
197 citations
TL;DR: In this article, the interfacial reaction between lead-free solder Sn-3.5Ag and electrolessly plated Ni-P metallization in terms of morphology and growth kinetics of the intermetallic compounds (IMC) is compared in order to clarify the role of P in the solder reaction.
Abstract: This work summarizes the interfacial reaction between lead-free solder Sn-3.5Ag and electrolessly plated Ni-P metallization in terms of morphology and growth kinetics of the intermetallic compounds (IMC). Comparison with pure Ni metallization is made in order to clarify the role of P in the solder reaction. During reflow, the IMCs formed with the Ni-P under-bump metallization (UBM) exist in chunky crystal blocks and small crystal agglomerates, while the ones with the sputtered Ni UBM exhibit uniformly scallop grains with faceted surfaces. The IMC thickness increases with reflow time following approximately a t1/3 power law for both systems. The IMC growth rate is higher with the Ni-P UBM than the Ni UBM. The thickness of the Ni3Sn4 layer increases linearly with the square root of thermal aging time, indicating that the growth of the IMCs is a diffusion-controlled process. The activation energy for Ni3Sn4 growth in solid-state reaction is found to be 110 kJ/mol and 91 kJ/mol for the Ni-P and sputtered Ni UBMs, respectively. Kirkendall voids are detected inside the Ni3P layer in the Sn-3.5Ag/Ni-P system. No such voids are found in the Sn-3.5Ag/Ni system.
83 citations
TL;DR: In this paper, the interfacial reaction of electroless Ni-P (EN) alloy and Ni UBMs with Sn-3.5Ag solder was investigated under different reflow durations.
79 citations
TL;DR: In this article, the growth rates of the main intermetallic compound (IMC), Ni3Sn4, at different aging temperatures are obtained and the activation energy calculated and the Kirkendall voids are found inside Ni3P layer after thermal aging in the solder/Ni-P UBM systems.
48 citations
TL;DR: In this paper, the effect of cooling rate on IMC growth is studied in Sn-3.5 Ag solder/Ni-P under bump metallization (UBM) system.
39 citations
TL;DR: In this paper, a field aided lateral crystallization of amorphous silicon has been carried out at 500 °C with an electric field of 200 V/cm, where large crystalline silicon grains with sizes over 100 μm have been formed in the laterally crystallized region.
9 citations
08 Dec 2004
TL;DR: In this paper, a novel method for making an integrated shadow mask used in fabrication of passive matrix OLED displays was reported, where positive and negative photoresists were employed to produce retrograded strip pillars with large overhang and undercut by photolithography, which serve as an effective shadow mask for patterning the organic layers and the metal cathodes in OLED display devices.
Abstract: This paper reports a novel method for making an integrated shadow mask used in fabrication of passive matrix OLED displays Common positive and negative photoresists were employed to produce retrograded strip pillars with large overhang and undercut by photolithography The pillar strips serve as an effective shadow mask for patterning the organic layers and the metal cathodes in OLED display devices It is expected that this method can significantly enhance the performance of passive matrix OLED at a low shadow mask fabrication cost The method can be used for fabricating more complicated structures for other display applications
3 citations
TL;DR: The optical properties of a hybrid aligned nematic liquid crystal (LC) device with three-electrode structure for fast response applications have been systematically studied in this article, where the highest transmittance is obtained by optimizing the electrode structure and the bias voltage for a certain cell gap and LC material.
Abstract: The optical properties of a new hybrid aligned nematic liquid crystal (LC) device (Jpn J Appl Phys 42 (2003) L763) with three-electrode structure for fast response applications have been systematically studied The transmission shows a clear dependence on the electrode structure, the bias voltage and LC material The highest transmittance is obtained by optimizing the electrode structure and the bias voltage for a certain cell gap and LC material The response time is dependent on LC material, but is not sensitive to the bias voltage and cell structure in our experiment
2 citations
TL;DR: In this article, an integral flexure that serves both the functions of a load beam and a gimbal for application in rotary actuators of hard disk drives (HDD) is presented.
Abstract: This paper presents a new design of an integral flexure that serves both the functions of a load beam and a gimbal for application in rotary actuators of hard disk drives (HDD). The design has optimized geometry that improves resonant frequency while retaining adequate rotational flexibility. Prototypes of the integral flexure are fabricated from a single piece of stainless-steel foil by photochemical machining techniques without involving welding and extra alignment. Its performance is simulated using finite element method and resonant frequencies of its prototype are measured. The numerical simulation and experimental results are in good agreement.
1 citations
18 Oct 2004
TL;DR: In this article, a 3D wafer-level hermetical packaging solution for microelectromechanical-system (MEMS) is presented, where the MEMS wafer is sandwiched between a top glass wafer and a bottom Si substrate wafer with the assistance of a gold intermediate layer.
Abstract: In this paper, a 3D wafer-level hermetical packaging solution for micro-electromechanical-system (MEMS) is presented The MEMS wafer is sandwiched between a top glass wafer and a bottom Si substrate wafer With the assistance of a gold intermediate layer, the bottom Si wafer is hermetically sealed to the MEMS wafer with 3D electric feed-through connecting the metal pads on MEMS wafer with solder balls or bonding pads on bottom wafer for flip chip process The bond strength is higher than 5 MPa