• Journal of Welding and Joining
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• 제16권4호
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• pp.92-97
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• 1998

Because of the low melting temperature of solder, each temperature cycle initiates an irrecoverable creep deformation at the solder interconnection which connects the package body with the PCB. The crack starts and propagates from the position where the creep deformation is maximized. This work has tried to compare and analyze the thermal fatigue life of solder interconnection which is affected by the lead material, the size of die pad, chip thickness, and interface delamination of 48-Pin TSOP under the temperature cycle ($0^{\circ}C$~1$25^{\circ}C$). The crack initiation position and thermal fatigue life which are calculated by using FEA method are well matched with the results of experiments. The thermal Fatigue life of copper lead frame is extended around 3.6 times longer than that of alloy 42 lead frame. It is maximized when the chip size is matched with the length of the lead. It tends to be extended as the thickness of chip got thinner. As the interfacial delamination between die pad and EMC is increased, the thermal fatigue life tends to decrease in the beginning of delamination, and increase after the delamination grew after 45% of the length of die pad.

• Corrosion Science and Technology
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• 제14권4호
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• pp.161-165
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• 2015

This paper presents an analysis of thermal stress induced along the interface between a polymeric coating layer and a steel substrate as a result of uniform temperature change. The epoxy layer is assumed to be a linear viscoelastic material and to be theromorheologically simple. The viscoelastic boundary element method is employed to investigate the behavior of interface stresses. The numerical results exhibit relaxation of interface stresses and large stress gradients, which are observed in the vicinity of the free surface. Since the exceedingly large stresses cannot be borne by the polymeric coating layer, local cracking or delamination can occur at the interface corner.

• 한국결정학회지
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• 제9권2호
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• pp.125-130
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• 1998

본 논문에서는 부직포를 삽입한 Gr/Ep 복합재료의 충격 흡수 특성을 연구하였다. 계면(interface) 층에 유리 부직포 또는 탄소 부직포를 삽입하여 복합적층판을 제작하였다. 저속충격 시험을 수행하였으며, 충격에 의한 층간분리(delamination)를 C-Scan과 현미경을 사용하여 관찰하였다. 실험결과 계면에 부직포를 삽입함으로써 충격에 의한 층간분리 면적이 감소함을 알 수 있었다.

• 한국안전학회지
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• 제33권2호
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• pp.8-13
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• 2018

The light weight composite materials have been replacing in high performance structures. The object of this study is to examine the effects of the initial crack location about a delamination in a PVC foam cored sandwich composite that is used for the strength improvement of structures. The initial crack location and fiber laminates thickness were changed with several types. The MMB specimen was used for evaluating the fracture toughness and crack behaviors. The material used in the experiment is a commercial twill carbon prepreg in CFRP material and Airex in PVC foam core. Sandwich laminate composites are composed by PVC foam core layer between CFRP face sheets. The face sheets were fabricated as 2 types of 5 and 8 plies. The initial cracks were located in a PVC form core and the interface of upper CFRP sheet. From the results, the crack initiation was affected with the location of the initial crack inserted in the PVC foam core. Among them, the initial crack at 1/3 of the upper part of the PVC foam core was the most rapid progression. And the critical energy release rate was $0.40kJ/m^2$, which is the lowest value when the initial crack was inserted into the interface between a PVC foam core and CFRP laminated with 5 plies. Meanwhile, the highest value of $1.27kJ/m^2$ was obtained when the initial crack was located at the center line in case of the 8 plies.

• 한국안전학회지
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• 제30권3호
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• pp.7-12
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• 2015

CFRP composites are used as primary structural members in various industrial fields because their specific strength and specific stiffness are excellent in comparison to conventional metals. Their usage is expanding to high added-value industrial fields because they are more than 50% lighter than metals, and have excellent heat resistance and wear resistance. However, when CFRP composites suffer impact damage, destruction of fiber and interface delamination occur. This causes an unexpected deterioration of strength, and for this reason it is very difficult to ensure the reliability of the excellent mechanical properties. Therefore, for the destruction mechanism in bending with impact damage, this study investigated the reinforcement data regarding various external loads by identifying the consequential strength deterioration. Specimens were damaged by impact with a steel ball propelled by air pressure. Decrease in bending strength caused by the tension and compression of the impact side, and depending on the lamination direction of fiber and interface inside the specimen. From the bending test it was found that the bending strength reduced when the impact energy increased. Especially in the case of compression on the impact side, as tensile stress occurred at the damage starting point, causing rapid failure and a substantially reduced failure strength.

• 접착 및 계면
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• 제22권2호
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• pp.69-77
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• 2021

세계적으로 지속가능한 세상을 만들기 위한 노력이 제조업에서 많이 이루어지고 있다. 이를 위해서는 사용 후 제품을 쉽고 간단하게 해체할 수 있는 설계 개념 중요하다. 접합된 제품 해체 시부품에 대한 피해가 없도록 접합부위가 분해되어 재활용이나 수리를 가능하게 하는 신기술이 최근 개발되고 있다. 본 총설에서는 조절가능한 접합-해체용 소재 기술, 특히 빛으로 해체하는 접착소재기술 동향을 정리하였다. 또한 반도체, 디스플레이 산업에 현재 활용되고 있는 빛 이용 임시 접합-해체용 필름에 대해 기술하였다.

• 한국분말재료학회지
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• 제26권4호
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• pp.319-326
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• 2019

Additive manufacturing (AM) is a highly innovative method for joining dissimilar materials for industrial applications. In the present work, AM of STS630 and Ti-6Al-4V powder alloys on medium entropy alloys (MEAs) NiCrCo and NiCrCoMn is studied. The STS630 and Ti64 powders are deposited on the MEAs. Joint delamination and cracks are observed after the deposition of Ti64 on the MEAs, whereas the deposition of STS630 on the MEAs is successful, without any cracks and joint delamination. The microstructure around the fusion zone interface is characterized by scanning electron microscopy and X-ray diffraction. Intermetallic compounds are formed at the interfacial regions of MEA-Ti64 samples. In addition, Vicker's hardness value increased dramatically at the joint interface between MEAs and Ti-6Al-4V compared to that between MEAs and STS630. This result is attributed to the brittle nature of the joint, which can lead to a decrease in the joint strength.

• 대한기계학회논문집A
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• 제26권5호
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• pp.835-842
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• 2002

In this paper, static and fatigue bending strengths and failure mechanisms of CFRP (carbon fiber reinforced plastics) laminates having impact damages have been evaluated. Composite laminates used for this experiment are CF/EPOXY orthotropy laminated plates, which have two-interfaces $[0^0_ 4/90^0_4]_{ sym}$. A steel ball launched by the air gun collides against CFRP laminates to generate impact damages. The damage growth during bending fatigue test is observed by the scanning acoustic microscope (SAM) and also, the fracture surfaces were observed by using the SEM (scanning electron microscope). In the case of impacted-side compression, fracture is propagated from the transverse crack generated near impact point. On the other hand, fracture is developed toward the impact point from the edge of interface-B delamination in the case of impacted-side tension. Eventually, failure mechanisms have been confirmed based on the observed delamination areas and fracture surfaces.

• 대한기계학회논문집A
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• 제24권4호
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• pp.946-954
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• 2000

The purposes of the paper are to calculate stresses and strains of the disk with overcoating layer rotating quickly under normal loading and shear loading by contacting with head and to present material properties preventing the delamination between the disk and overcoating layer. The hard disk is modeled as two-layered disk composed with overcoating layer and the rest layers and the loading onto the disk is assumed axisymmetric. Solutions to equilibrium equations and compatibility equations are derived with the form of polynimial and Bessel function and coefficients satisfying boundary conditions are obtained differently for the case of body force, normal force and shear force. The risk of delamination are investigated for us to calculate the differences of strains at the interface between the disk and overcoating layer and the material properties preventing delamination are presented by calculating the differences of strains according to Young's modulus and density of disk.

• 한국공작기계학회논문집
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• 제10권6호
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• pp.48-56
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• 2001

In this paper, this study aims at the evaluation on the characteristics of CFRP laminate plates using a falling weight impact tester. The experiment was conducted on several laminates of different orientation. A system was built far measur- ing the impact strength of CFRP laminates in consideration of stress wave propagation theory using a falling weight impact tester. Delamination areas of impacted specimens for the different ply orientation were measured with ultrasonic C- scanner to find correlation between impact energy and delamination area. Absorbed energy of quasi-isotropic specimen having flour interfaces was higher than that of orthotropic laminates with two interfaces. The more interfaces, the greater the energy absorbed. The absorbed energy oft hybrid specimen containing a GFRP layer was higher than that of normal specimens.