MATERIALS TRANSACTIONS
Online ISSN : 1347-5320
Print ISSN : 1345-9678
ISSN-L : 1345-9678
Component Candidacy of Second Side Reflow with Lead-Free Solder
Yueli LiuDavid A. GeigerDongkai Shangguan
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2006 Volume 47 Issue 6 Pages 1577-1583

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Abstract

For double-sided assemblies, the solder joints on the topside of the board are inverted and reflowed again. During the second reflow, the components are held in place by the surface tension, which may prevent the components from falling off under the gravitational force. A method is needed to determine a component’s candidacy for bottom-side attachment based on the component weight and total pad area.
In this paper, a theoretical model was introduced to determine the critical value for component fall-off during the second reflow. Design of Experiments (DOE) and ANOVA analysis for lead-free solder boards were performed to examine the main process factors which have different effects on the component fall-off for different components, and comparison was made between lead-free and SnPb solders. Optical inspection and cross-sectioning were carried out for further investigation. The test results indicated no significant difference of CgPa value between SnPb and lead-free solders.

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© 2006 The Japan Institute of Metals and Materials
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