• Korean Journal of Materials Research
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• v.3 no.3
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• pp.282-291
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• 1993

Joining ${Al}_{2}{O}_{3}$ and STS 304 stainless steel by active metal brazing method with using CuI Owt % Ti and Cu -7 .5wt % Zr insert metal, their interfaces were analyzed and strength of the joint brazed with Cu-7.5wt % Zr insert metal also investigated with shear strength testing method. In brazing with Cu-lOwt% Ti insert metal, the single reaction layer was formed by the reaction with Ti and ${Al}_{2}{O}_{3}$ at the interface between ${Al}_{2}{O}_{3}$ and insert metal, but the double reaction layer was found in brazing with Cu-7.5wt % Zr insert metal because of the difference of their wettability on the surface of ${Al}_{2}{O}_{3}$. Fracture shear strength about 86MPa was obtained from ${Al}_{2}{O}_{3}$/Cu-7.5wt% Zr/STS 304 stainless steel joint and reasonable strength of the joints is attributed to the formation of double reaction layer at the interface.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2011.05a
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• pp.187-187
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• 2011

지르코니아 ($ZrO_2$) 표면에 금속 (Au)으로 표면 코팅한 후 Ti-6Al-4V와 진공 브레이징 접합을 행하였다. 표면에 코팅한 Au 층의 영향을 비교 분석하기 위하여 Au를 코팅하지 않은 지르코니아도 모재로 사용하였다. 접합소재로는 Ag-Cu-Ti계 active filler를 사용하였다. $ZrO_2$/Ti-6Al-4V 브레이징 결과, active filler는 양측 모재 표면에 wetting 되었으며, Ti-6Al-4V 내부로 filler 확산으로 인하여 두 모재의 direct joint가 관찰되었다. 접합 계면 사이에 접합부 결함은 관찰되지 않았다.

• Korean Journal of Materials Research
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• v.9 no.10
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• pp.962-969
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• 1999

Elastic and elasto-plastic stress analyses of AlN/Cu and AlN/W pints produced by active-metal brazing method using Ag-Cu-Ti insert-metal were performed with use of Finite-Element-Method(FEM). The results of stress analyses were compared with those from the pint strength tests and the observations of fracture behaviors. It was shown that a remarkably larger maximum principal stress is built in the AlN/Cu pint compared to the A1N/ W joint. Especially, the stress concentration with tensile component was confirmed at the free surface close to the bonded interface of AlN/Cu. The elasto-plastic analysis under consideration of stress relaxation effect of Ag-Cu-Ti insert possessing a so-called 'soft-metal effect' showed that the insert leads to a lowering of maximum principal stress in AlNiCu pint, even though an increase of the insert thickness above 100$\mu\textrm{m}$ could not bring its further decrease. The maximum pint strengths measured by shear test were 52 and 108 MPa for AlNiCu and AlN/W pints. respectively. Typical fractures of AlN/Cu pints occurred in a form of 'dome' which initiated from the free surface of AlN close to the bonded interface and proceeded towards the AlN inside forming a large angle. AlN/W pints were usually fractured at AlN side along the interface of AlN/insert-metal.

• Korean Journal of Materials Research
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• v.3 no.1
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• pp.33-42
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• 1993

Abstract The increasing application of $Al_2$,$O_3$ and related ceramics as engineering materials is because of their attractive properties of fine ceramics. One solution to the wide variety of ceramic to metal combination lies in the effective joining. Active metal brazing of $Al_2$,$O_3$, to STS304 was investigated using Cu -Ti alloys. Titanium additive is chosen since it is good oxide former~. Brazing is performed under vacuum($10^{-3}$-$10^{-4}$ torr), a temperature between 1100 and 120$0^{\circ}C$ and time of 0.5-1.5hr. The microstructure of the brazed joints of $Al_2$,$O_3$ to STS304 with Cu-Ti insert metals were examined by using optical microscope and SEM and reaction products were analyzed by using EDX, WDX and XRD. Also interfacial reactions occuring during the brazing of $Al_2$,$O_3$/Cu-Ti/STS304 system are discussed. Experimental results showed formation of Titanium oxide T$i_2$$O_3$ which is attributable to the joining $Al_2$,$O_3$ to STS304 with Cu-Ti insert metal.

• Korean Journal of Materials Research
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• v.10 no.10
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• pp.703-708
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• 2000

As the engine design changes to get high efficiency and performance of commercial diesel engine, surface w wear of the earn follower becomes an important issue as applied load increasing at the contact face between cam follower and cam. We developed the ceramic cam follower made of sili$\infty$n nitride ceramic which was more wear resistant than the cast iron or sintered metal cam follower. Ceramic cam follower was made by direct brazing of thin ceramic disk to steel body using an active brazing alloy without the interlayer. In-situ crowning(R), resulted from the difference of thermal expansion coefficient between ceramic and carbon steel after direct brazing without any stress-relieving inter]ayer, could be controlled. When a earbon steel was heated above $A_{c1}$ point and then c$\infty$led, the expansion curve represented a hysteresis. Appropriate crowning was achieved below the $A_{c1}$ point(about $723^{\circ}C$) and crowning increased with brazing temperature exponentially above the $A_{c1}$ point. Optimum brazing temperature range was from 700 to $720^{\circ}C$. We developed successfully the ceramic cam follower having appropriate crowning and being inexpensive. Also we could successfully control the crowning of ceramic earn follower by hysteresis behavior of thermal expansion of earbon steel during direct brazing process.

• The Journal of Korean Academy of Prosthodontics
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• v.50 no.3
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• pp.169-175
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• 2012

Purpose: In this study, brazing characteristics of $ZrO_2$ and Ti-6Al-4V brazed joints with increasing temperature were investigated. Materials and methods: The sample size of the $ZrO_2$ was $3mm{\times}3mm{\times}3mm$ (thickness), and Ti-6Al-4V was $10mm(diameter){\times}5mm(thickness)$. The filler metal consisted of Ag-Cu-Sn-Ti was prepared in powder form. The brazing sample was heated in a vacuum furnace under $5{\times}10^{-6}$ torr atmosphere, while the brazing temperature was changed from 700 to $800^{\circ}C$ for 30 min. Results: The experimental results shows that brazed joint of $ZrO_2$ and Ti-6Al-4V occurred at $700-800^{\circ}C$. Brazed joint consisted of Ag-rich matrix and Cu-rich phase. A Cu-Ti intermetallic compounds and a Ti-Sn-Cu-Ag alloy were produced along the Ti-6Al-4V bonded interface. Thickness of the reacted layer along the Ti-6Al-4V bonded interface was increased with brazing temperature. Defect ratios of $ZrO_2$ and Ti-6Al-4V bonded interfaces decreased with brazing temperature. Conclusion: Thickness and defect ratio of brazed joints were decreased with increasing temperature. Zirconia was not wetting with filler metal, because the reaction between $ZrO_2$ and Ti did not occur enough.

• Journal of the Korean Ceramic Society
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• v.35 no.3
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• pp.219-230
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• 1998

Various interlayer materials have been tested for active metal(Cusil ABA) brazing of Si3N4/S. S316 joint. In general multilayer joint had higher strength(80-150 MPa) and better reliability than monolayered one. The joint with Cu(0.2)/Mo(0.3)/Cu(0.2mm) interlayer showed the highest bending strength of abou 490 MPa and the joint with Cu(0.2)/Mo(0.3mm) interlayer the best reliability (14.6 Weibull modulus). The stresses distributed in joint materials during 4-point bending test were estimated by CAE von Mises analysis; the estimated stresses were In good agreement with the measured data. In multilayer joint Cu was though to reduce the residual stresses induced by the difference in thermal expansion coefficient between the ceramic Mo and metal It apperared that a Cu/Mo was optimum interlayer material for Si3N4/S. S316 joint with high bending strength (420 MPa) and reliability. In addition the various shapes and types of compound were examined by EPMA in joining interface.

• Journal of the Microelectronics and Packaging Society
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• v.26 no.3
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• pp.15-22
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• 2019

In these days, importance of the power electronic devices and modules keeps increasing due to electric vehicles and energy saving requirements. However, current silicon-based power devices showed several limitations. Therefore, wide band gap (WBG) semiconductors such as SiC, GaN, and $Ga_2O_3$ have been developed to replace the silicon power devices. WBG devices show superior performances in terms of device operation in harsh environments such as higher temperatures, voltages and switching speed than silicon-based technology. In power devices, the reliability of the devices and module package is the critically important to guarantee the normal operation and lifetime of the devices. In this paper, we reviewed the recent trends of the power devices based on WBG semiconductors as well as expected future technology. We also presented an overview of the recent package module and fabrication technologies such as direct bonded copper and active metal brazing technology. In addition, the recent heat management technologies of the power modules, which should be improved due to the increased power density in high temperature environments, are described.

• Korean Journal of Materials Research
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• v.9 no.10
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• pp.970-977
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• 1999

Effect of Mo interlayer on the relaxation of residual stress in AlN/Cu pint bonded by active-metal brazing method was investigated. The stress analyses by finite-element-method, the measurement of pint strength and the observation of fracture surface were carried out and their results were compared with each other. From the results of stress analysis it is confirmed that a Mo interlayer led to a shift of maximum stress concentration site from AlN/insert-metal interface$\rightarro$ insert-metal/Mo$\rightarro$Mo interlayer. Additionally, with increase of the Mo interlayer thickness the stress concentration with tensile component was separately built both at the interface of Cu/Mo and AlN/Mo. whereby the residual stress in the free surface of AlN close to the bonded interface was drastically reduced. The AlN/Mo/Cu pints with Mo interlayer thickness of above 400$\mu\textrm{m}$ showed the strengths higher than 200 MPa. upto max. 275 MPa, while the AlN/Cu pint only max. 52 MPa.