• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.23 no.3
• /
• pp.237-242
• /
• 2014

Recently much research are has been done into the compositions of lead-free solders. As a result, there has been a rapid increase in the number of new compositions. In the past, the properties of these new compositions were determined and verified through drop-impact tests. However, these drop tests were expensive and it took a long time to obtain a result. The main goal of this study was to establish an analytical method capable of predicting the impact life-time of a new solder composition for board-level flip chips though the application of drop simulations using LS-DYNA. Based on the reaction load obtain with LS-DYNA, the drop-impact fracture cycles were predicted. The study was performed using a Sn-3.0Ag-0.5Cu solder (305 composition). To verify the reliability of the proposed analytical method, the results of the drop-impact tests and life-time analysis were compared, and were found to be in good agreement. Thus, the new analytical method was shown to be very useful and effective.

• PNF and Movement
• /
• v.19 no.2
• /
• pp.279-285
• /
• 2021

Purpose: This study aimed to develop new digital navicular drop test (ND-NDT) equipment and to determine its validity and reliability. Methods: A total of 24 healthy male and female adults, who fully understood the purpose of the study and gave consent to participate in the study, were selected as participants. The NDT and ND-NDT were conducted in the dominant foot of the participants in a random order. For the NDT, the position of the navicular bone was marked with a pen first; then, the height of the navicular bone from the ground was measured in both sitting and standing positions. For the ND-NDT, after the sticker-type reflection markers were attached to the position of the navicular bone, the height of the navicular bone from the ground was measured in both sitting and standing positions. To assess the validity of the diagnostic tests, the same examiner measured the height of the medial longitudinal arch (MLA) three times in both the sitting and standing positions. To assess the inter-rater reliability of the ND-NDT, three examiners, in a random order, attached the sticker-type reflection markers to the position of the navicular bone and then measured the height of the MLA in both positions. Results: In the sitting position, the Pearson correlation coefficient (r) between the two diagnostic tests was very high (r = 0.97) and statistically significant. In the standing position, the Pearson correlation coefficient (r) between the two tests was 0.95, which was also statistically significant. The ICC_2,1 values in the sitting and standing positions were 0.93 and 0.95, respectively, indicating significantly high inter-rater reliability. Conclusion: The ND-NDT equipment showed very high diagnostic validity, as well as excellent inter-rater reliability, indicating the clinical usefulness of the equipment as a diagnostic system for confirming pes planus.

• The Transactions of the Korean Institute of Electrical Engineers P
• /
• v.63 no.4
• /
• pp.266-270
• /
• 2014

In this paper, the effects of superconducting fault current limiter (SFCL) installed in power distribution system on reliability are evaluated and analyzed. The fault current will be decreased in power distribution system with SFCL because of the increased impedance of SFCL. The decreased fault current will improve the voltage drop of the bus of substation. The voltage drop is an important factor of power distribution system reliability. In this paper, improvement of reliability worth is analyzed when SFCLs are installed at the starting point in power distribution system. First, resistor-type SFCL model is used in PSCAD/EMTDC. Next, typical power distribution system is modeled. Finally, when the SFCLs with impedance 0.5 [${\Omega}$] are installed in feeder, power distribution system reliability is evaluated. Also, the improvement effect of reliability worth including the effect of voltage sag is analyzed using customer interruption cost according to whether or not SFCL is installed.

• Journal of the Microelectronics and Packaging Society
• /
• v.17 no.3
• /
• pp.65-69
• /
• 2010

In this study, we investigated the effects of UBM(Under Bump Metallization) and solder composition on the drop impact reliability of wafer level packaging. Fan-in type WLP chips were prepared with different solder ball composition (Sn3.0Ag0.5Cu, and Sn1.0Ag0.5Cu) and UBM (Cu 10 ${\mu}m$, Cu 5 ${\mu}m$\Ni 3 ${\mu}m$). Drop test was performed up to 200 cycles with 1500G acceleration according to JESD22-B111. Cu\Ni UBM showed better drop performance than Cu UBM, which could be attributed to suppression of IMC formation by Ni diffusion barrier. SAC105 was slightly better than SAC305 in terms of MTTF. Drop failure occurred at board side for Cu UBM and chip side for Cu\Ni UBM, independent of solder composition. Corner and center chip position on the board were found to have the shortest drop lifetime due to stress waves generated from impact.

• Journal of the Korean Society for Precision Engineering
• /
• v.24 no.10
• /
• pp.99-108
• /
• 2007

As the structure of a mobile phone becomes thin to catch up with a slim product trend, the reliability of a LCD module is on the rise as a big issue for a product design. A drop test is the most basic and important verification method for a mechanical quality control but it requires much time and cost during a product development process. Thus many manufacturers have considered design guide lines using CAE and simulation for more effective usage of limited resources on the market. In this paper, the Maximum Principle Stress of a LCD glass panel is calculated on the basis of explicit FE Analyses method and input conditions are determined according to the general test standard. The design guideline for reliability improvements are suggested on the basis of the results of FE Analysis.

• Journal of the Korean Society of Industry Convergence
• /
• v.22 no.3
• /
• pp.381-385
• /
• 2019

In this Study, as the structure of smart phone display becomes thin to catch up with slim product trend, the reliability of display module is on the rise as a issue for product design. Especially, almost part of cellular phone should undergo drop test when they fall 1.5m above ground. Thus many manufacturers have considered design guide line using CAE and simulation for more efficive usage of limited resources om the martket. This test simulates the case when cellular phone slips through user's flingers while he is talking on the phone. This paper studies a drop simulation of glass for display in smart phone. This design for reliability improvements are suggested on the basis of the results of FE Analysis and display of smart phone design.

• The Journal of Korean Physical Therapy
• /
• v.31 no.3
• /
• pp.147-150
• /
• 2019

Purpose: The purpose of this study was to compare the reliability of unilateral hip abductor strength assessment in side-lying with break and make test in subjects with pelvic drop. Hip abduction muscles are very important in the hip joint structures. Therefore, it is essential to evaluate their strength in a reliable way. Methods: Twenty-five subjects participated in this study. Unilateral isometric hip abductor muscle strength was measured in side-lying, with use of a specialized tensiometer using smart KEMA system for make test, of a hand held dynamometer for break test. Coefficients of variation, and intra class correlation coefficients were calculated to determine test-retest reliability of hip abductor strength. Results: In make test, maximal hip abductor strength in the side-lying position was significantly higher compared with break test (p<0.05). Additionally, Test-retest reliability of hip abductor strength measurements in terms of coefficients of variation (3.7% for make test, 16.1% for break test) was better in the side-lying position with make test. All intraclass correlation coefficients with break test were lower than make test (0.90 for make test, 0.73 for break test). Conclusion: The side-lying body position with make test offers more reliable assessment of unilateral hip abductor strength than the same position with break test. Make test in side-lying can be recommended for reliable measurement of hip abductor strength in subjects with pelvic drop.

• Proceedings of the Korean Reliability Society Conference
• /
• 2005.06a
• /
• pp.339-348
• /
• 2005

In evaluation of electronic reliability on the PCB(Printed Circuit Board),electrochemical migration is one of main test objects. The phenomenon of electrochemical migration occurs In the environment of the high humidity and the high temperature under bias through a continuous aqueous electrolyte. In this paper, the generating mechanism of electrochemical migration is investigated by using water drop acceleration test under various waters. The waters used in the water drop test are city water, distilled water and ionic water. It found that the generated velocity o of electrochemical migration depended on the temperature of water and the electrolyte quantity which included in the various waters.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
• /
• 2007.11a
• /
• pp.225-229
• /
• 2007

The output voltage of a synchronous generator is regulated constantly by field current control of excitation system. Synchronous generator exciter has two type, first one is Drop control type by thyristor and second one is exciter current control type through power output by PWM control. Control method of the second one prevails, but when the power devices have a breakdown, output voltage of the generator rises rapidly. This exciter must have a protection circuit and system is complicated, so reliability is poor Excitation control type which is drop control type control only 10% of the power, so it can be improved precision. When a trouble come to the controller, output voltage of a generator don't rise excessively and the voltage rise about 10%, so it has a excellent reliability. This paper prove stability of the digital AVR.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2010.06a
• /
• pp.315-315
• /
• 2010

휴대용 전자 기기는 얇고 가벼우면서 빠른 대용량을 처리하는 속도와 다기능이 필요한 추세로 가고 있다. 기기 크기가 작아짐에 따라서 내장 되는 칩 또한 소형화, 고집적화, 고성능화가 요구되므로 이에 상응하는 발전된 패키징 기술이 필요하게 되었고, 이에 대응하기위해서 embedded components device 패키징 기술이 필요로 하게 되었다. 본 연구에서는 $21{\Omega}$ 의 저항 값을 갖는 1005 수동 소자를 prepreg를 이용하여 PCB기판에 내장 한 후 micro via를 이용하여 무전해 구리 도금으로 전기적인 연결을 하여 기판을 제작하였다. 제작되어진 기판으로 Reflow, Aging 테스트 후 칩과 계면간의 금속화합물 반응을 관찰하였다. 또한 Reflow외 시효처리를 끝마친 기판을 사용하여 drop test를 실시한 후 fail 발생 시 저항 값의 변화와 접합부의 미세조직을 관찰하였다.