• Title/Summary/Keyword: bumps

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A Study on the Optimization of IR Laser Flip-chip Bonding Process Using Taguchi Methods (다구찌법을 이용한 IR 레이저 Flip-chip 접합공정 최적화 연구)

  • Song, Chun-Sam;Ji, Hyun-Sik;Kim, Joo-Han;Kim, Jong-Hyeong;Ahn, Hyo-Sok
    • Journal of Welding and Joining
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    • v.26 no.3
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    • pp.30-36
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    • 2008

  • A flip-chip bonding system using IR laser with a wavelength of 1064 nm was developed and associated process parameters were analyzed using Taguchi methods. An infrared laser beam is designed to transmit through a silicon chip and used for transferring laser energy directly to micro-bumps. This process has several advantages: minimized heat affect zone, fast bonding and good reliability in the microchip bonding interface. Approximately 50 % of the irradiated energy can be directly used for bonding the solder bumps with a few seconds of bonding time. A flip-chip with 120 solder bumps was used for this experiment and the composition of the solder bump was Sn3.0Ag0.5Cu. The main processing parameters for IR laser flip-chip bonding were laser power, scanning speed, a spot size and UBM thickness. Taguchi methods were applied for optimizing these four main processing parameters. The optimized bump shape and its shear force were modeled and the experimental results were compared with them. The analysis results indicate that the bump shape and its shear force are dominantly influenced by laser power and scanning speed over a laser spot size. In addition, various effects of processing parameters for IR laser flip-chip bonding are presented and discussed.

  • https://doi.org/10.5781/KWJS.2008.26.3.030 인용 PDF KSCI

Performance Predictions of Gas Foil Bearing with Leaf Foils Supported on Bumps (범프로 지지되는 다엽 포일을 갖는 가스 포일 베어링의 성능 해석)

  • Kim, T.H.;Mun, H.W.
    • Tribology and Lubricants
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    • v.34 no.3
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    • pp.75-83
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    • 2018

  • Microturbomachinery (< 250 kW) using gas foil bearings can function without oil lubricants, simplify rotor-bearing systems, and demonstrate excellent rotordynamic stability at high speeds. State-of-the-art technologies generally use bump foil bearings or leaf foil bearings due to the specific advantages of each of the two types. Although these two types of bearings have been studied extensively, there are very few studies on leaf-bump foil bearings, which are a combination of the two aforementioned bearings. In this work, we illustrate a simple mathematical model of the leaf-bump foil bearing with leaf foils supported on bumps, and predict its static and dynamic performances. The analysis uses the simple elastic model for bumps that was previously developed and verified using experimental data, adds a leaf foil model, and solves the Reynolds equation for isothermal, isoviscous, and ideal gas fluid flow. The model predicts that the drag torques of the leaf-bump foil bearings are not affected significantly by static load and bearing clearance. Due to the preload effect of the leaf foils, rotor spinning, even under null static load, generates significant hydrodynamic pressure with its peak near the trailing edge of each leaf foil. A parametric study reveals that, while the journal eccentricity and minimum film thickness decrease, the drag torque, direct stiffness, and direct damping increase with increasing bump stiffness. The journal attitude angle and cross-coupled stiffness remain nearly constant with increasing bump stiffness. Interestingly, they are significantly smaller compared to the corresponding values obtained for bump foil bearings, thus, implying favorable rotor stability performance.

  • https://doi.org/10.9725/kts.2018.34.3.75 인용 PDF KSCI

Improvement of Reliability of COG Bonding Using In, Sn Bumps and NCA (NCA 물성에 따른 극미세 피치 COG (Chip on Glass) In, Sn 접합부의 신뢰성 특성평가)

  • Chung Seung-Min;Kim Young-Ho
    • Journal of the Microelectronics and Packaging Society
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    • v.13 no.2 s.39
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    • pp.21-26
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    • 2006

  • We developed a bonding at low temperature using fine pitch Sn and In bumps, and studied the reliability of the fine pitch In-Sn solder joints. The $30{\mu}m$ pitch Sn and In bumps were joined together at $120^{\circ}C$. A non conductive adhesive (NCA) was applied during solder joining. Thermal cycling test ($0^{\circ}C-100^{\circ}C$, 2 cycles/h) of up to 2000 cycles was carried out to evaluate the reliability of the solder joints. The bondability was evaluated by measuring the contact resistance (Rc) of the joints through the four point probe method. As the content of filler increased, the reliability improved in the solder joints during thermal cycling test because the contact resistance increased little. The filler redistributed the stress and strains from the thermal shock over the entire joint area.

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