• Journal of Welding and Joining
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• 제21권6호
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• pp.46-54
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• 2003

The thermal response of electronic assemblies during forced convection-infrared reflow soldering is studied. Soldering for attaching electronic components to printed circuit boards is performed in a process oven that is equipped with porous panel heaters, through which air is injected in order to dampen temperature fluctuations in the oven which can be established by thermal buoyancy forces. Forced convection-infrared reflow soldering process with air injection is simulated using a 2-dimensional numerical model. The multimode heat transfer within the reflow oven as well as within the electronic assembly is simulated. Parametric study is also performed to study the effects of various conditions such as conveyor speed, blowing velocity, and electronic assembly emissivity on the thermal response of electronic assemblies. The results of this study can be used in the process oven design and selecting the oven operating conditions to ensure proper solder melting and solidification.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2006년 제4회 한국유체공학학술대회 논문집
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• pp.561-564
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• 2006

Because of new requirements related to the employment of SMT(Surface Mounting Technology) manufacturing and the diversity of components on high density PCB(printed circuit boards), Thermal control of the reflow process is required in oder to achieve acceptable yields and reliability of SMT assemblies. Accurate control of the temperature distribution during the reflow process is one of the major requirements, especially in lead-free assembly. This study has been performed for reflow process using the commercial CFD tool(Fluent) for predicting flow and temperature distributions. There was flow recirculation region that had a weak point in the temperature uniformity. Porous plate was installed to prevent and minimize flow recirculation region for acquiring uniform temperature in oven. This paper provided design concept from CFD results of the steady state temperature distribution and flow field inside a reflow oven.

• Journal of Welding and Joining
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• 제15권6호
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• pp.105-115
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• 1997

A numerical study is performed to predict the thermal response of a detailed card assembly during infrared reflow soldering. The card assembly is exposed to discontinuous infrared panel heater temperature distributions and high radiative/convective heating and cooling rates at the inlet and exit of the oven. The convective, radiative and conduction heat transfer within the reflow oven as well as within the card assembly are simulated and the predictions illustrate the detailed thermal responses. The predictions show that mixed convection plays an important role with relatively high frequency effects attributed to buoyancy forces, however the thermal response of the card assembly is dominated by radiation. The predictions of the detailed card assembly thermal response can be used to select the oven operating conditions to ensure proper solder melting and minimization of thermally induced card assembly tresses and warpage.

• 반도체디스플레이기술학회지
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• 제5권3호
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• pp.29-32
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• 2006

Because of new requirements related to the employment of SMT(Surface Mounting Technology) manufacturing and the diversity of components on high density PCB(Printed Circuit Boards), Thermal control of the reflow process is required in order to achieve acceptable yields and reliability of SMT assemblies. Accurate control of the temperature distribution during the reflow process is one of the major requirements, especially in lead-free assembly. This study has been performed for reflow process using the commercial CFD(Computational Fluid Dynamics) tool for predicting flow and temperature distributions. Porous plate was installed to prevent leakage flow which was one of the major problem of temperature uniformity in the reflow process. There is a separation region where the flow is turned. Outside wall made of porous plate is to prevent and minimize separation region for acquiring uniform temperature during operation. This paper provided design concept from CFD results of the steady state temperature distribution and flow field inside a reflow oven.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.1063-1068
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• 2004

A numerical study is performed to predict the effect of operating conditions on the thermal response of electronic assemblies during infrared reflow soldering. The multimode heat transfer within the reflow oven as well as within the electronic assembly is simulated, and the predictions illustrate the detailed thermal responses. Parametric study is performed to determine the thermal response of electronic assemblies to various conditions such as conveyor speed, exhaust velocity, and component emissivity. The predictions of the detailed electronic assembly thermal response can be used in selecting the oven operating conditions to ensure proper soldering and minimization of thermally-induced electronic assembly stresses.

• 설비공학논문집
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• 제14권1호
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• pp.1-9
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• 2002

The thermal response of electronic components during infrared reflow soldering is studied by a two-dimensional numerical model. The convective, radiative and conduction heat transfer within the reflow oven as well as within the card assembly are simulated. Parametric study is also performed to determine the thermal response of electronic components to various conditions such as conveyor velocities, exhaust velocities and emissivities. The results of this study can be used in selecting the oven operating conditions to ensure proper solder melting and minimization of thermally induced card assembly stresses.

• 한국마이크로전자및패키징학회:학술대회논문집
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• 한국마이크로전자및패키징학회 2000년도 Proceedings of 5th International Joint Symposium on Microeletronics and Packaging
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• pp.17-17
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• 2000

The issue of reflow profiling continues to be a complex topic. The pains often associated with profiling can be reduced greatly if certain guidelines are followed and if there is a strong understanding of the variables that can be encountered during the reflow process. This paper shall discuss the appropriate guidelines and trouble shooting methods for reflow profiling, and in particular shall focus upon the benefits of implementing the linear ramp-to-spike profile. Delta T(T) is defined as the variation of temperature found on an assembly during the reflow process. Too large of a T can result in soldering defects, so to combat T a Ramp-Soak-Spike(RSS) reflow profile often is utilized. However, when using a newer-style reflow oven, the T often is minimized or eliminated, thus, the soak zone of the reflow profile becomes an unnecessary step. Because of this, the implementation of a linear Ramp-To-Spike(RTS) reflow profile should be considered. Benefits such as reduced energy costs, reduced solder defects, increased efficiency, improved wetting, and a simplification of the reflow profile process may be experienced when using the RTS profile. Included in this paper are the suggested process parameters for setting up the RSS and RTS profiles and the chemical and metallurgical reactions that occur at each set point of these profiles. The paper concludes with a discussion and pictures of several profile-related defects. Each of these defects is described, analyzed, and instructions are given for troublshooting these defects.

• 마이크로전자및패키징학회지
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• 제15권4호
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• pp.1-7
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• 2008

본 실험에서는 두가지 리플로 시스템에 따라 솔더 범프 내에 생성되는 금속간 화합물의 성장거동에 대하여 연구하였다. 산화막이 증착된 Si 기판 위에 직류 마그네트론 스퍼터링을 이용하여 Ti(50 nm), Cu($1{\mu}m$), Au(50 nm), Ti(50 nm)의 박막을 형성한 후, 전해 도금을 이용하여 $5{\mu}m$두께의 Cu 범프와 $20{\mu}m$ 두께의 Sn 범프를 형성하였다. 급속열처리장치(RTA)와 일반 리플로를 이용하여 전해 도금으로 형성된 Sn($20{\mu}m$)/Cu($5{\mu}m$) 범프를 동일한 온도에서 각각 리플로 공정을 진행한 결과, 급속열처리장치를 이용하여 리플로를 할 때, 플럭스를 사용하지 않고 범프로 형성할 수 있었으며, 솔더 계면에 형성된 금속간 화합물이 일반 리플로의 경우보다 더 얇게 형성되었다.

• 한국광학회:학술대회논문집
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• 한국광학회 2000년도 제11회 정기총회 및 00년 동계학술발표회 논문집
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• pp.192-193
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• 2000

We studied the characteristics and fabricated the plano-convex refractive microlenses using the thermal reflow method. The exposed resist was resolved in a standard developing process. The remaining resist of circle pattern was melted in an oven 12$0^{\circ}C$ to 15$0^{\circ}C$. The shape of the melted resist microlenses is ruled by surface tension. Diameter and hight of the fabricated microlenses were 250${\mu}{\textrm}{m}$ to 325${\mu}{\textrm}{m}$ and 15${\mu}{\textrm}{m}$ to 22${\mu}{\textrm}{m}$, respectively. The surface profile was calculated using data curve-fitting method with circle equation. The optical characteristics was analysed using optical simulation program.

• 한국마이크로전자및패키징학회:학술대회논문집
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• 한국마이크로전자및패키징학회 2001년도 Proceedings of 6th International Joint Symposium on Microeletronics and Packaging
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• pp.45-47
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• 2001

Due to pressure from threatened legislation in Europe, consumer and governmental pressure in Japan, and glob머 market considerations in the US, there is a rapidly growing interest in lead-free solderinger, Although the move to lead free soldering seems inevitable, many problems will arise in production assembly. It is generally acknowledged that the lead-free solders available offer a much s smaller process window than lead/tin, related mainly to the higher soldering temperatures which naturally result from increases of liquidus temperatures of at least 300 C. However, raising reflow temperatures from the current 220-2300 C to 250 2600 C will lead to problems with the boards and components as well as i increasing oxidation effects. There is a need to keep reflow temperatures low without reducing solderablity. Some results on benefits of inert atmospheres are discussed in this paper. For example, testing in a nitrogen atmosphere, with 300 ppm oxygen, by the N National Physical Laboratory (NPU has revealed clear benefits for ine$\pi$mg lead-free alloys, by restoring the solderability to lead/tin levels, by enabling lower soldering temperatures. However, there has been little testing over a range of oxygen levels in nitrogen and this is an important issue in determining n nitrogen supply and oven costs. Some results are reported here from work by NPL conducted for BOC in w which solderability was evaluated for tin기ead and tin/silver/copper eutectic a alloys in a wetting balance over a range of oxygen levels form 10 ppm to 21% ( (air). The studies confirm that acceptable wetting times occur in inert atmospheres a at soldering temperatures 20 to 300 C lower than are possible in air.