• Title/Summary/Keyword: Electronic packaging

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Effect of Reflow Number and Surface Finish on the High Speed Shear Properties of Sn-Ag-Cu Lead-free Solder Bump (리플로우 횟수와 표면처리에 따른 Sn-Ag-Cu계 무연 솔더 범프의 고속전단 특성평가)

  • Jang, Im-Nam;Park, Jai-Hyun;Ahn, Yong-Sik
    • Journal of the Microelectronics and Packaging Society
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    • v.16 no.3
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    • pp.11-17
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    • 2009
  • The drop impact reliability comes to be important for evaluation of the life time of mobile electronic products such as cellular phone. The drop impact reliability of solder joint is generally affected by the kinds of pad and reflow number, therefore, the reliability evaluation is needed. Drop impact test proposed by JEDEC has been used as a standard method, however, which requires high cost and long time. The drop impact reliability can be indirectly evaluated by using high speed shear test of solder joints. Solder joints formed on 3 kinds of surface finishes OSP (Organic Solderability Preservation), ENIG (Electroless Nickel Immersion Gold) and ENEPIG (Electroless Nickel Electroless Palladium Immersion Gold) was investigated. The shear strength was analysed with the morphology change of intermetallic compound (IMC) layer according to reflow number. The layer thickness of IMC was increased with the increase of reflow number, which resulted in the decrease of the high speed shear strength and impact energy. The order of the high speed shear strength and impact energy was ENEPIG > ENIG > OSP after the 1st reflow, and ENEPIG > OSP > ENIG after 8th reflow.

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Manufacturing of Metal Micro-wire Interconnection on Submillimeter Diameter Catheter (서브-밀리미터 직경의 카테터 표면 위 금속 마이크로 와이어 접착 공정)

  • Jo, Woosung;Seo, Jeongmin;Kim, Taek-Soo
    • Journal of the Microelectronics and Packaging Society
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    • v.24 no.2
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    • pp.29-35
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    • 2017
  • In this paper, we investigated a manufacturing process of metal micro-wire interconnection on submillimeter diameter catheter. Over the years, flexible electronic researches have focused on flexible plane polymer substrate and micro electrode manufacturing on its surface. However, a curved polymer substrate, such as catheter, is very important for medical application. Among many catheters, importance of submillimeter diameter steerable catheter is increasing to resolve the several limitations of neurosurgery. Steering actuators have been researched for realizing the steerable catheter, but there is no research about practical wiring for driving these actuators. Therefore we developed a new manufacturing process for metal micro-wire interconnection on submillimeter diameter catheter. We designed custom jigs for alignment of the metal micro-wires on the submillimeter diameter catheter. An UV curing system and commercial products were used to reduce the manufacturing time and cost; Au micro-wire, UV curable epoxy, UV lamp, and submillimeter diameter catheter. The assembled catheter was characterized by using an optical microscope, a resistance meter, and a universal testing machine.

Development of Polymer Elastic Bump Formation Process and Bump Deformation Behavior Analysis for Flexible Semiconductor Package Assembly (유연 반도체 패키지 접속을 위한 폴리머 탄성범프 범핑 공정 개발 및 범프 변형 거동 분석)

  • Lee, Jae Hak;Song, Jun-Yeob;Kim, Seung Man;Kim, Yong Jin;Park, Ah-Young
    • Journal of the Microelectronics and Packaging Society
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    • v.26 no.2
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    • pp.31-43
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    • 2019
  • In this study, polymer elastic bumps were fabricated for the flexible electronic package flip chip bonding and the viscoelastic and viscoplastic behavior of the polymer elastic bumps according to the temperature and load were analyzed using FEM and experiments. The polymer elastic bump is easy to deform by the bonding load, and it is confirmed that the bump height flatness problem is easily compensated and the stress concentration on thin chip is reduced remarkably. We also develop a spiral cap type and spoke cap type polymer elastic bump of $200{\mu}m$ diameter to complement Au metal cap crack phenomenon caused by excessive deformation of polymer elastic bump. The proposed polymer elastic bumps could reduce stress of metal wiring during bump deformation compared to metal cap bump, which is completely covered with metal wiring because the metal wiring on these bumps is partially patterned and easily deformable pattern. The spoke cap bump shows the lowest stress concentration in the metal wiring while maintaining the low contact resistance because the contact area between bump and pad was wider than that of the spiral cap bump.

3D Porous Foam-based Triboelectric Nanogenerators for Energy Harvesting (3차원 기공구조를 이용한 정전기반 에너지 하베스팅 나노발전기 소자제조)

  • Jeon, Sangheon;Jeong, Jeonghwa;Hong, Suck Won
    • Journal of the Microelectronics and Packaging Society
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    • v.26 no.1
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    • pp.9-15
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    • 2019
  • Here, we present a facile route to fabricate a vertically stacked 3D porous structure-based triboelectric nanogenerator (TENG) that can be used to harvest energy from the friction in a repetitive contact-separation mode. The unit component of TENG consists of thin Al foil electrodes integrated with microstructured 3D foams such as Ni, Cu, and polyurethane (PU), which provide advantageous tribo-surfaces specifically to increase the friction area to the elastomeric counter contact surfaces (i.e., polydimethylsiloxane, PDMS). The periodic contact/separation-induced triboelectric power generation from a single unit of the 3D porous structure-based TENG was up to $0.74mW/m^2$ under a mild condition. To demonstrate the potential applications of our approach, we applied our TENGs to small-scale devices, operating 48 LEDs and capacitors. We envision that this energy harvesting technology can be expanded to the applications of sustainably operating portable electronic devices in a simple and cost-effective manner by effectively harvesting wasted energy resources from the environment.

Interfacial and Mechanical Properties of Sn-57Bi-1Ag Solder Joint with Various Conditions of a Laser Bonding Process (다양한 레이저 접합 공정 조건에 따른 Sn-57Bi-1Ag 솔더 접합부의 계면 및 기계적 특성)

  • Ahn, Byeongjin;Cheon, Gyeong-Yeong;Kim, Jahyeon;Kim, Jungsoo;Kim, Min-Su;Yoo, Sehoon;Park, Young-Bae;Ko, Yong-Ho
    • Journal of the Microelectronics and Packaging Society
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    • v.28 no.2
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    • pp.65-70
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    • 2021
  • In this study, interfacial properties and mechanical properties of joints were reported after Cu pads finished with organic solderability preservative (OSP) on flame retardant-4 (FR-4) printed circuit board (PCB) and electronic components were joined with a Sn-57Bi-1Ag solder paste by using a laser bonding process. The laser bonding process was performed under various bonding conditions with changing a laser power and a bonding time and effects of bonding conditions on interfacial and mechanical properties of joints were analyzed. In order to apply for industry, properties of bonding joints using a reflow bonding process which are widely used were compared. When the laser bonding process were performed, we observed that Cu6Sn5 intermetallic compounds (IMCs) were fully formed at the interface although the bonding times were very short about 2 and 3 s. Furthermore, void formations of the joints by using the laser bonding process were suppressed at the joints with comparing to the reflow bonding process and shear strengths of bonding joints were higher than that by using the reflow bonding process. Therefore, in spite of a very short bonding time, it is expected that joints will be stably formed and have a high mechanical strength by using the laser bonding process.

Design of EMI Reduction of SMPS Using MLCC Filters (MLCC를 이용한 SMPS의 EMI 저감 설계)

  • Choi, Byeong-In;Choa, Sung-Hoon
    • Journal of the Microelectronics and Packaging Society
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    • v.27 no.4
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    • pp.97-105
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    • 2020
  • Recently, as the data speed and operating frequencies of Ethernet keeps increasing, electro magnetic interference (EMI) also becomes increasing. The generation of such EMI will cause malfunction of near electronic devices. In this study, EMI filters were applied to reduce the EMI generated by DC-DC SMPS (switching mode power supply), which is the main cause of EMI generation of Ethernet switch. As the EMI filter, MLCCs with excellent withstanding voltage characteristics were used, which had advantages in miniaturization and mass production. Two types of EMI MLCC filters were used, which are X-capacitor and X, Y-capacitor. X-capacitor was composed of 2 MLCCs with 10 nF and 100 nF capacity and 1 Mylar capacitor. Y-capacitor was consisted of 6 MLCCs with a capacity of 27 nF. When only X-capacitor was applied as EMI filter, the conductive EMI field strength exceeded the allowable limit in frequency range of 150 kHz ~ 30 MHz. The radiative EMI also showed high EMI strength and very small allowable margin at the specific frequencies. When the X and Y-capacitors were applied, the conductive EMI was greatly reduced, and the radiation EMI was also found to have sufficient margin. In addition, X, Y-capacitors showed very high insulation resistance and withstanding resistance performances. In conclusion, EMI X, Y-capacitors using MLCCs reduced the EMI noise effectively and showed excellent electrical reliability.

Laser Transmission Welding of Flexible Substrates and Evaluation of the Mechanical Properties (플렉서블 기판의 레이저 투과 용접 및 기계적 특성 평가)

  • Ko, Myeong-Jun;Sohn, Minjeong;Kim, Min-Su;Na, Jeehoo;Ju, Byeong-Kwon;Park, Young-Bae;Lee, Tae-Ik
    • Journal of the Microelectronics and Packaging Society
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    • v.29 no.2
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    • pp.113-119
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    • 2022
  • In order to improve the mechanical reliability of next-generation electronic devices including flexible, wearable devices, a high level of mechanical reliability is required at various flexible joints. Organic adhesive materials such as epoxy for bonding existing polymer substrates inevitably have an increase in the thickness of the joint and involve problems of thermodynamic damage due to repeated deformation and high temperature hardening. Therefore, it is required to develop a low-temperature bonding process to minimize the thickness of the joint and prevent thermal damage for flexible bonding. This study developed flexible laser transmission welding (f-LTW) that allows bonding of flexible substrates with flexibility, robustness, and low thermal damage. Carbon nanotube (CNT) is thin-film coated on a flexible substrate to reduce the thickness of the joint, and a local melt bonding process on the surface of a polymer substrate by heating a CNT dispersion beam laser has been developed. The laser process conditions were constructed to minimize the thermal damage of the substrate and the mechanism of forming a CNT junction with the polymer substrate. In addition, lap shear adhesion test, peel test, and repeated bending experiment were conducted to evaluate the strength and flexibility of the flexible bonding joint.

Enhanced Thermoelectric Properties in n-Type Bi2Te3 using Control of Grain Size (Grain 크기 조절을 통한 n-Type Bi2Te3 열전 소재 특성 향상)

  • Lee, Nayoung;Ye, Sungwook;Jamil Ur, Rahman;Tak, Jang-Yeul;Cho, Jung Young;Seo, Won Seon;Shin, Weon Ho;Nam, Woo Hyun;Roh, Jong Wook
    • Journal of the Microelectronics and Packaging Society
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    • v.28 no.4
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    • pp.91-96
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    • 2021
  • The enhancement of thermoelectric figure of merit was achieved by the simple processes of sieving and high energy ball milling, respectively, which are enable to reduce the grain size of n-type Bi2Te3 thermoelectric materials. By optimizing the grain size, the electrical conductivities and thermal conductivities were controlled. In this study, spark plasma sintering was employed for hindering the grain growth during the sintering process. The thermoelectric figure of merit was measured to be 0.78 in the samples with 30 min high energy ball milling process. Notably, this value was 40 % higher than that of pristine Bi2Te3 sample. This result shows the properties of thermoelectric materials can be readily controlled by optimization of grain size via simple ball milling process.

Flexible Planar Heater Comprising Ag Thin Film on Polyurethane Substrate (폴리우레탄 유연 기판을 이용한 Ag 박막형 유연 면상발열체 연구)

  • Seongyeol Lee;Dooho Choi
    • Journal of the Microelectronics and Packaging Society
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    • v.31 no.1
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    • pp.29-34
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    • 2024
  • The heating element utilizing the Joule heating generated when current flows through a conductor is widely researched and developed for various industrial applications such as moisture removal in automotive windshield, high-speed train windows, and solar panels. Recently, research utilizing heating elements with various nanostructures has been actively conducted to develop flexible heating elements capable of maintaining stable heating even under mechanical deformation conditions. In this study, flexible polyurethane possessing excellent flexibility was selected as the substrate, and silver (Ag) thin films with low electrical resistivity (1.6 μΩ-cm) were fabricated as the heating layer using magnetron sputtering. The 2D heating structure of the Ag thin films demonstrated excellent heating reproducibility, reaching 95% of the target temperature within 20 seconds. Furthermore, excellent heating characteristics were maintained even under mechanically deforming environments, exhibiting outstanding flexibility with less than a 3% increase in electrical resistance observed in repetitive bending tests (10,000 cycles, based on a curvature radius of 5 mm). This demonstrates that polyurethane/Ag planar heating structure bears promising potential as a flexible/wearable heating element for curved-shaped appliances and objects subjected to diverse stresses such as human body parts.

A Study on the Phase Change of Cubic Bi1.5Zn1.0Nb1.5O7(c-BZN) and the Corresponding Change in Dielectric Properties According to the Addition of Li2CO3 (Li2CO3 첨가에 따른 입방정 Bi1.5Zn1.0Nb1.5O7(c-BZN)의 상 변화 및 그에 따른 유전특성 변화 연구)

  • Yuseon Lee;Yunseok Kim;Seulwon Choi;Seongmin Han;Kyoungho Lee
    • Journal of the Microelectronics and Packaging Society
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    • v.30 no.4
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    • pp.79-85
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    • 2023
  • A novel low-temperature co-fired ceramic (LTCC) dielectric, composed of (1-4x)Bi1.5Zn1.0Nb1.5O7-3xBi2Zn2/3Nb4/3O7-2xLiZnNbO4 (x=0.03-0.21), was synthesized through reactive liquid phase sintering of Bi1.5Zn1.0Nb1.5O7-xLi2CO3 ceramic at temperatures ranging from 850℃ to 920℃ for 4 hours. During sintering, Li2CO3 reacted with Bi1.5Zn1.0Nb1.5O7, resulting in the formation of Bi2Zn2/3Nb4/3O7, and LiZnNbO4. The resulting sintered body exhibited a relative sintering density exceeding 96% of the theoretical density. By altering the initial Li2CO3 content (x) and consequently modulating the volume fraction of Bi1.5Zn1.0Nb1.5O7, Bi2Zn2/3Nb4/3O7, and LiZnNbO4 in the final sintered body, a sample with high dielectric constant (εr), low dielectric loss (tan δ), and the temperature coefficient of dielectric constant (TCε) characterized by NP0 specification (TCε ≤ ±30 ppm/℃) was achieved. As the Li2CO3 content increased from x=0.03 mol to x=0.15 mol, the volume fraction of Bi2Zn2/3Nb4/3O7 and LiZnNbO4 in the composite increased, while the volume fraction of Bi1.5Zn1.0Nb1.5O7 decreased. Consequently, the dielectric constant (εr) of the composite materials varied from 148.38 to 126.99, the dielectric loss (tan δ) shifted from 5.29×10-4 to 3.31×10-4, and the temperature coefficient of dielectric constant (TCε) transitioned from -340.35 ppm/℃ to 299.67 ppm/℃. A dielectric exhibiting NP0 characteristics was achieved at x=0.09 for Li2CO3, with a dielectric constant (εr) of 143.06, a dielectric loss (tan δ) value of 4.31×10-4, and a temperature coefficient of dielectric constant (TCε) value of -9.98 ppm/℃. Chemical compatibility experiment with Ag electrode revealed that the developed composite material exhibited no reactivity with the Ag electrode during the co-firing process.