• Title/Summary/Keyword: interfacial fracture toughness

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Determination of the Failure Paths of Leadframe/EMC Joints

  • Lee, H.Y.;Kim, S.R.
    • Journal of the Korean institute of surface engineering
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    • v.33 no.4
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    • pp.241-250
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    • 2000
  • Popcorn cracking phenomena frequently occur in thin plastic packages during the solder reflow process, which are definitely affected by poor adhesion of Cu-based leadframe to epoxy molding compounds (EMCs). In the present work, in order to enhance the adhesion strength, a brown-oxide treatment on the Cu-based leadframe was carried out and the adhesion strength of leadframe/EMC interface was measured in terms of fracture toughness by using sandwiched double-cantilever beam (SDCB) specimens. After the adhesion tests, fracture surfaces were analyzed by SEM, AES, EDS and AFM to make the failure path clear. Results showed that failure path was closely related to the oxidation time and the interfacial fracture toughness.

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Effect of surface toughness on the interfacial adhesion energy between glass wafer and UV curable polymer for different surface roughness (표면거칠기에 따른 글래스 웨이퍼와 UV 경화 폴리머사이의 계면접착 에너지 평가)

  • Jang, Eun-Jung;Hyun, Seoung-Min;Choi, Dae-Geun;Lee, Hak-Joo;Park, Young-Bae
    • Proceedings of the KSME Conference
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    • 2008.11a
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    • pp.40-44
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    • 2008
  • The interfacial adhesion energy between resist and a substrate is very important due to resist pull-off problems during separation of mold from a substrate in nanoimprint process. And effect of substrate surface roughness on interfacial adhesion energy is very important. In this paper, we have treated glass wafer surface using $CF_4$ gas for increase surface roughness and it has tested interfacial adhesion properties of UV resin/glass substrate interfaces by 4 point bending test. The interfacial adhesion energies by bare, 30, 60 and 90 sec surface treatments are 0.62, 1.4, 1.36 and 2 $J/m^2$, respectively. The test results showed quantitative comparisons of interfacial fracture energy (G) effect of glass wafer surface roughness.

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The fractal analysis of the fracture surface of concretes made from different coarse aggregates

  • Prokopski, Grzegorz;Konkol, Janusz
    • Computers and Concrete
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    • v.2 no.3
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    • pp.239-248
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    • 2005
  • The article presents the results of examination of the fractal dimension D of concrete specimen fracture surfaces obtained in fracture toughness tests. The concretes were made from three different types of coarse aggregate: gravel, dolomite and basalt aggregate. Ordinary concretes (C40) and high-performance concretes (HPC) were subjected to testing after 7, 14, 28 and 90 days of curing, respectively. In fracture toughness and compressive tests, different behaviours of concretes were found, depending on the type of aggregate and class of concrete (C40, HPC). A significant increase in the strength parameters tested occurred also after a period of 28 days (up to the $90^{th}$ day of curing) and was particularly large for concretes C40. Fractal examinations performed on fracture replicas showed that the fractal dimension D was diverse, depending on the coarse aggregate type and concrete class being, however, statistically constant after 7 and 14 days for respective concretes during curing. The fractal dimension D was the greater, the worse strength properties were possessed by the concrete. A cross-grain crack propagation occurred in that case, due to weak cohesion forces at the coarse aggregate/mortar interface. A similar effect was observed for C40 and HPC made from the same aggregate. A greater dimension D was exhibited by concretes C40, in which case the fracture was easier to form compared with high-performance concretes, where, as a result of high aggregate/mortar cohesion forces, the crack propagation was of inter-granular type, and the resulted fracture was flatter.

A Study on the Surface Treatment of Prepreg with $Ar^+$ Ion to Increase Mode I Fracture Characteristics of Fiber-Reinforced Composites (섬유강화 적층복합재의 열림모드 파괴특성 향상을 위해 $Ar^+$ 이온도움반응법을 적용한 프리프레그의 표면처리 연구)

  • Lee, Gyeong-Yeop;Ji, Chang-Heon;Yang, Jun-Ho
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.24 no.11
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    • pp.2771-2776
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    • 2000
  • In this work, the effect of surface treatment of prepreg on the mode I fracture behavior was studied. Unidirectional (0-deg) double cantilever beam (DCB) specimens were used for fracture tests. Two groups of DCB specimens were made: the first group was made of prepregs surface-treated by Ar(sup)+ ion beam under oxygen environment and the second group was made of regular prepregs. For both groups, fracture resistance curve (R-curve) was determined and compared to each other, Results showed that resistance behavior of the first group is better than that of the second group. That is, mode I fracture toughness, G(sub)Ic of the first group is 24% larger than that of the second group. SEM examination shows that the improvement of G(sub)Ic is due to the increase of interfacial strength between plies.

Improvement of Adhesion Strength between Cu-based Leadframe and Fpoxy Molding Compound

  • Lee, Ho-Yoing
    • Transactions on Electrical and Electronic Materials
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    • v.1 no.3
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    • pp.23-28
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    • 2000
  • A block-oxide layer was formed on the surface of Cu-based leadframe by chamical oxidation method in order to enhance the adhesion strength between Cu-based leadframe and epoxy molding compound (EMC) Using sandwiched double cantilever beam (SDCB) specimens, the adesion strength was measured in terms of interfacial fracture toughness, G$\sub$IC//Results showed that the black-oxide layer was composed of two kinds of layers: pebble-like Cu$_2$O layer and acicular CuO layer, At the initial stage of oxidation the Cu$_2$O layer was preferentially formed and thickened up to around 200 nm whithin 1 minute of the oxidation time. Then the CuO layer started to from atop of the Cu$_2$O layer and thickened up to around 1300 nm until 20 minutes. As soon as the CuO layer formed, the thickness of Cu$_2$O layer began to reduce and finally reached to around 150 nm. The pre-cleaned and the Cu$_2$O coated leadframes showed almost no adhesion of EMC, however, as the CuO precipitates appeared and became continuous, G$\sub$IC/ increased up to around 80 J/㎡. Further oxidation raised G$\sub$IC/ up. to around 100 J/㎡.

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Mechanical Behaviors of CFRP Laminate Composites Reinforced with Aluminum Oxide Powder

  • Kwon, Oh-Heon;Yun, Yu-Seong;Ryu, Yeong-Rok
    • Journal of Power System Engineering
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    • v.18 no.6
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    • pp.166-173
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    • 2014
  • In this study, a laminated composite material with dispersing aluminum oxide powder between the CFRP laminate plies, and also CFRP composites without aluminium oxide powder were fabricated for Mode I experiments using the DCB specimen and a tensile test. The behavior of the crack and the change of the interfacial fracture toughness were evaluated. Also in order to evaluate the damage mechanism for the crack extension, the AE sensor on the surface of the DCB test specimen was attached. AE amplitude was estimated for CFRP-alumina and CFRP composite. And the fracture toughness was evaluated by the stress intensity factor and energy release rate. The results showed that an unstable crack was propagated rapidly in CFRP composite specimen along with the interface, but crack propagation in CFRP-alumina specimen was relatively stable. From results, we show that aluminium oxide powder spreaded uniformly in the interface of the CFRP laminate carried out the role for preventing the sudden crack growth.

Impact behavior of including the boundary between A356/SiCw and Al alloy (Al alloy와의 경계면을 포함한 A356/SiCw의 충격거동)

  • 조종인;남현욱;한경섭
    • Proceedings of the Korean Society For Composite Materials Conference
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    • 2002.05a
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    • pp.97-100
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    • 2002
  • In this research, the impact behavior of the boundary between MMC-reinforced SiC whisker and Al alloy were studied. It is known that the resultant of the interfacial reaction between SiC whisker and Al alloy has brittle and low toughness property. In this paper, impact behavior of graded MMC & Al alloy shows the interfacial opening at the boundary. Generally this phenomenon is generated by thermal residual stress, brittle interfacial reaction resultant and difference of the deflection. So, these results may be interpreted as a macroscopic method of measuring the interfacial strength between matrix and reinforcement

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Effect of Interlayer Thickness on Mechanical Properties of Nicalon-Fiber-Reinfored SiC Composites (Nicalon 섬유강화 SiC 복합재료에서 섬유 Coating층의 두께가 기계적 성질에 미치는 영향)

  • 김민수;김영욱;이준근;정덕수
    • Journal of the Korean Ceramic Society
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    • v.30 no.7
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    • pp.549-556
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    • 1993
  • Interfacial shear strength plays an important role in determining the mechanical properties of a fiber-reinforced ceramic composites. In this study, the effect ofinterlayer thickness on mechanical properties of Nicalon-fiber-reinforced SiC composites fabricated via polymer solution infiltration/chemical vapor infiltration (PSI/CVI) was studied. It was found that the flexural strength and fracture toughness of the composites were increased with the interlayer thickness and showed maximum value at the interlayer thickness of 0.66${\mu}{\textrm}{m}$. Typical flexural strength and fracture toughness of Nicalon-fiber-reinforced SiC composites with interlayer thickness of 0.66${\mu}{\textrm}{m}$ were 391.7$\pm$34.6MPa and 15.1$\pm$1.8MPa.m1/2, respectively.

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The Aging Effect of $Avimid^(R)$ K3B/1M7 Laminates in $80^{\circ}C$ Water ($Avimid^(R)$ K3B/IM7 복합재료의 $80^{\circ}C$ 물에서의 노화현상)

  • Kim Hyung-Won
    • Journal of the Korean Society of Propulsion Engineers
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    • v.9 no.4
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    • pp.23-30
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    • 2005
  • The Hygrothermal aging of the laminates of $Avimid^(R)$ K3B/IM7 in $80^{\circ}C$ water was studied as a function of immersion time prior to forming microcracks. The factors causing the $80^{\circ}C$ water to degradation of the laminates could be the degradation of the matrix toughness, the change in residual stresses or the interfacial damage between the fiber and the matrix. The times to saturation in $80^{\circ}C$ water for the laminates and for the neat resin were 100 hours and 500 hours. After 500 hours aging of the neat resin, the glass transition temperature was changed less than 1% by DSC test, and the weight gain was 1.55% increase with the diffusion coefficient $7\times10^{-6}m/s^2$ and the fracture toughness was decreased about 41%. After 100 hours fully saturated aging of the ${[+45/0/-45/90]}_s$ K3B/IM7 laminates in $80^{\circ}C$ water, the weight gain was 0.41% increase with the diffusion coefficient $1\times10^{-6}m/s^2$. In 100 hours, the loss of the fracture toughness of the laminates was 43.8% of the original toughness by the microcracking fracture toughness criterion. Therefore, the main factor to degrade the microcracking toughness of the laminates could be the degradation of the matrix fracture toughness.

Effects of Carbon-coated SiC Whiskers on the Mechanical Properties of SiC Whisker Reinforced Silicon Nitride Ceramic Composite (SiC 휘스커 강화 질화규소 복합재료의 기계작 성질에 미치는 카본 코팅 SiC 휘스커의 영향)

  • 배인경;이영규;조원승;최상욱;장병국;임실묵
    • Journal of the Korean Ceramic Society
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    • v.36 no.10
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    • pp.1007-1015
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    • 1999
  • The Si3N4 composites reinforced with carbon-coated SiC whiskers were fabricated by hot-pressing at 180$0^{\circ}C$ for 2 hours to examine the effects of carbon-coated whiskers on the mechanical properties of SiC whisker reinforced Si3N4 composites. The flexural strength of the Si3N4 composites and Si3N4 monolith respectively. The weak interfacial bond between carbon-coated SiC whiskers and Si3N4 matrix which enhances the crack deflection and whisker pull-out could contribute to the improvement of mechanical properties of the composites.

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