• International Journal of Korean Welding Society
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• v.4 no.1
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• pp.61-66
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• 2004

In this paper, the effect of underfill packages was investigated by numerical approach and experimental test. Reliability improvement was the main issue in the package technology. BGA, CSP and small-sized packages, have problems due to concentration of the stress in solder joints. One of the latest technologies to overcome is underfill encapsulant. Mainly, it is noticed the effect of the underfill in the packages. The predicted thermal fatigue lifes are performed by Coffin-Manson's equation with ANSYS (v.5.62). Also, thermal cycle test during from 218K to 423K was included. Finally we could find that underfill greatly reduce the concentration stress in solder joint, thus the fatigue life was improved than without underfill.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2005.05a
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• pp.437-442
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• 2005

In this paper, we proposed the 2-dimensional inspection algorithm for micro-BGA(Ball Grid Array) device using a vision system. The proposed method uses the subpixel algorithm for high precision. The proposed algorithm preferentially extracts the package area of device in the input image. After the extraction of package area, each ball areas are extracted by ball search window method. The parameters for inspection are calculated for the extracted ball area. In the simulation results, we have the average error within $17{\mu}m$.

• Journal of the Microelectronics and Packaging Society
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• v.15 no.4
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• pp.65-70
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• 2008

The mechanical shear strength of BGA(Ball Grid Array) solder joints under high impact loading was investigated. The Sn-37Pb solder balls with a diameter of $500{\mu}m$ were placed on the pads of FR-4 substrates with ENIG(Electroless Nickel Immersion Gold) surface treatment and reflowed. For the High Temperature Storage(HTS) test, the samples were aged a constant testing temperature of $120^{\circ}C$ for up to 250h. After the HTS test, high speed shear tests with various shear speed of 0.01, 0.1, 1, 3 m/s were conducted. $Ni_3Sn_4$ intermetallic compound(IMC) layer was observed at the solder/Ni-P interface and thickness of IMC was increased with aging process. The shear strength increased with increasing shear speed. The fracture surfaces of solder joints showed various fracture modes dependent on shear speed and aging time. Fracture mode was changed from ductile fracture to brittle fracture with increasing shear speed.

• Korean Journal of Materials Research
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• v.10 no.12
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• pp.799-806
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• 2000

Cu$_{6}$Sn$_{5}$-dispersed 63Sn-37Pb solder bumps of 760$\mu\textrm{m}$ size were fabricated on Au(0.5$\mu\textrm{m}$)/Ni(5$\mu\textrm{m}$)/Cu(27$\pm$20$\mu\textrm{m}$) BGA substrates by screen printing process, and their shear strength were characterized with variations of dwell time at reflow peak temperature and aging time at 15$0^{\circ}C$ . With dwell time of 30 seconds at reflow peak temperature, the solder bumps with Cu$_{6}$Sn$_{5}$ dispersion exhibited higher shear strength than the value of the 63Sn-37Pb solder bump. With increasing the dwell time longer than 60 seconds, however the shear strength of the Cu$_{6}$Sn$_{5}$-dispersed solder bumps became lower than that the 63Sn-37Pb solder bumps. The failure surface of the solder bumps could be divided into two legions of slow crack propagation and critical crack propagation. The shear strength of the solder bumps was inversely proportional to the slow crack propagation length, regardless of the dwell time at peak temperature, aging time at 150 $^{\circ}C$ and the volume fraction of Cu$_{6}$Sn$_{5}$ dispersion.> 5/ dispersion.

• Journal of the Microelectronics and Packaging Society
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• v.9 no.4
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• pp.1-9
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• 2002

The metallurgical reaction properties between the pad consisted of 0.5 $\mu\textrm{m}$Au/5 $\mu\textrm{m}$Ni/Cu layers on a conventional ball grid array (BGA) substrate and In-15 (wt.%)Pb-5Ag solder ball were characterized during the reflow process and solid aging. During the reflow process of 1 to 5 minutes, it was observed that thin $AuIn_2$ or Ni-In intermetallic layer was formed at the interface of solder/pad. The dissolution rate of the Au layer into the molten solder was about $2\times 10^{-3}$ $\mu\textrm{m}$/sec which is remarkably low in comparison with a eutectic Sn-37Pb solder. After solid aging treatment for 500 hrs at $130^{\circ}C$, the thickness of $Ni_{28}In_{72}$ intermetallic layer was increased to about 3 $\mu\textrm{m}$ in all the conditions nevertheless the initial reflow time was different. These result show that In atoms in the solder alloy were diffused through the $AuIn_2$ phase to react with underlaying Ni layer during solid aging treatment. From the microstructural observation and shear tests, the reaction properties between In-15Pb-5Ag alloy and Au/Ni surface finish were analyzed not to trigger Au-embrittlement in the solder joints unlike Sn-37Pb composition.

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2002.09a
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• pp.219-225
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• 2002

This paper presents a novel "bumpless flip chip package"for cost! performance driven devices. Using the conventional electroplating and etching processes, this package enables the production of fine pitch BGA up to 256 I/O with single layer routing. An array of circuitry down to $25-50{\mu}{\textrm}{m}$ line/space is fabricated to fan-in and fan-out of the bond pads without using bumps or substrate. Various types of joint methods can be applied to connect the fine trace and the bond pad directly. The resin-filled terminal provides excellent compliancy between package and the assembled board. More interestingly, the thin film routing is similar to wafer level packaging whereas the fan-out feature enables high lead count devices to be accommodated in the BGA format. Details of the design concepts and processing technology for this novel package are discussed. Trade offs to meet various cost or performance goals for selected applications are suggested. Finally, the importance of design integration early in the technology development cycle with die-level and system-level design teams is highlighted as critical to an optimal design for performance and cost.

• The KIPS Transactions:PartA
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• v.10A no.4
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• pp.389-396
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• 2003

InfiniBand technology is being accepted as the future system interconnect to serve as the high-end enterprise fabric for cluster computing. This paper presents the design and implementation of the InfiniBand system interconnect, focusing on an InfiniBand host channel adapter (HCA) based on dual ARM9 processor cores The HCA is an SoC tailed KinCA which connects a host node onto the InfiniBand network both in hardware and in software. Since the ARM9 processor core does not provide necessary features for multiprocessor configuration, novel inter-processor communication and interrupt mechanisms between the two processors were designed and embedded within the KinCA chip. Kinch was fabricated as a 564-pin enhanced BGA (Bail Grid Array) device using 0.18${\mu}{\textrm}{m}$ CMOS technology Mounted on host nodes, it provides 10 Gbps outbound and inbound channels for transmit and receive, respectively, resulting in a high-performance cluster system.

• Journal of the Microelectronics and Packaging Society
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• v.6 no.3
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• pp.9-18
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• 1999

In this study, Metallugical properties between Sn-3.5Ag, Sn-37Pb eutectic solders and Au/Ni/cu substrate according to time span above the melting point were investigated. A conventional reflow soldering machine wert used for this study and time span above the melting point was determined by changing peak soldering temperature and conveyor speed. As results, scallop type intermetallic compounds of $Ni_3Sn_4$ were formed at joint interface and no Cu-Sn compounds were found at all; Ni layer performed as a barrier for Cu diffusion. As the peak soldering temperature increased, thickness of the intermetallic compound layer increased; maximum thickness of the scallop-layer was 2.2$\mu\textrm{m}$. The shape of scallops were transformed from hemi-sphere type to elliptical shape with smaller size. Micro-hardness of the solder joint decreased as the eutectic structure of Sn-3.5Ag and Sn-37Pb increased.

• Journal of Ship and Ocean Technology
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• v.9 no.4
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• pp.35-46
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• 2005

The performance of optimisation methods, based on penalty functions, is highly problem- dependent and many methods require additional tuning of some variables. This additional tuning is the influences of penalty coefficient, which depend strongly on the degree of constraint violation. Moreover, Binary-coded Genetic Algorithm (BGA) meets certain difficulties when dealing with continuous and/or discrete search spaces with large dimensions. With the above reasons, Real-coded Micro-Genetic Algorithm (R$\mu$GA) is proposed to find the global optimum of continuous and/or discrete nonlinear constrained engineering problems without handling any of penalty functions. R$\mu$GA can help in avoiding the premature convergence and search for global solution-spaces, because of its wide spread applicability, global perspective and inherent parallelism. The proposed R$\mu$GA approach has been demonstrated by solving three different engineering design problems. From the simulation results, it has been concluded that R$\mu$GA is an effective global optimisation tool for solving continuous and/or discrete nonlinear constrained real­world optimisation problems.

• Journal of the Microelectronics and Packaging Society
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• v.7 no.3
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• pp.55-61
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• 2000

Sn-37Pb and Sn-3.5Ag-0.7Cu solder balls of 0.3 mm diameter were reflow soldered with the variation of soldering peak temperature and conveyer speed of reflow machine. The peak temperatures far soldering were changed in the range of 220~$240^{\circ}C$ for Sn-37Pb and 230~$260^{\circ}C$ for Sn-3.5Ag-0.7Cu. As the results of experiments, optimum soldering condition for Sn-37Pb was $230^{\circ}C$ of soldering temp., 0.7~0.8 m/min of conveyer speed. The optimum condition for the Sn-3.5Ag-0.7Cu was $250^{\circ}C$ and 0.6 m/min. The maximum shear strength for the soldered joints of Sn-37Pb was 555 gf and of Sn-3.5Ag-0.7Cu was 617 gf. Thickness of the intermetallic compound Cu6Sn5 on the soldered interface was 1.13~1.45 $\mu\textrm{m}$ for Sn-37Pb and 2.5~4.3 $\mu\textrm{m}$ for Sn-3.5Ag-0.7Cu.