• Proceedings of the International Microelectronics And Packaging Society Conference
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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.

• Journal of Welding and Joining
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• 제30권5호
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• pp.64-69
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• 2012

Sn-Bi eutectic alloy has been widely used as one of the key solder materials for step soldering at low temperature. The Sn-58Bi solder paste containing chloride flux was adopted to compare with that using the chloride-free flux. The paste was applied on the electroless nickel-immersion gold (ENIG) surface finish by stencil printing, and the reflow process was then performed at $170^{\circ}C$ for 10 min. After reflow, the solder joints were aged at $125^{\circ}C$ for 100, 200, 300, 500 and 1000 h in an oven. The interfacial microstructures were obtained by using scanning electron microscopy (SEM), and the composition of intermetallic compounds (IMCs) was analyzed using energy dispersive spectrometer (EDS). Two different IMC layers, consisting of $Ni_3Sn_4$ and relatively very thin Sn-Bi-Ni-Au were formed at the solder/surface finish interface, and their thickness increased with increasing aging time. The wettability of solder joints was investigated by wetting balance test. The mechanical property of each aging solder joint was evaluated by the ball shear test in accordance with JEDEC standard (JESD22-B117A). The results show that the highest shear force was measured when the aging time was 100 h, and the fracture mode changed from ductile fracture to brittle fracture with increasing aging time. On the other hand, the chloride flux in the solder paste did not affect the shear force and fracture mode of the solder joints.