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Title: Inspection of micro-solderballs on a semiconductor bumped wafer using optical shadowgraph
Authors: Tay, C.J. 
Wang, S.H. 
Quan, C. 
Keywords: Height inspection
Image processing
Micro-ball grid array (micro-BGA)
Optical shadowgraph
Wafer bump inspection
Issue Date: Apr-2004
Citation: Tay, C.J., Wang, S.H., Quan, C. (2004-04). Inspection of micro-solderballs on a semiconductor bumped wafer using optical shadowgraph. Optical Engineering 43 (4) : 963-970. ScholarBank@NUS Repository.
Abstract: We describe a simple way to effectively measure the height of a micro-solderball of a micro-ball grid array (micro-BGA) on a bumped wafer. The proposed method derived using a white-light illumination source can perform a speedy whole field inspection of the micro-solderballs. The optical system consists of a white-light telecentric configuration and a long-working-distance microscope with a telecentric objective. The optical axes of the illuminating light and microscope are symmetrically arranged with respect to the normal of the test surface and hence the technique is applicable to optical measurement on a mirror-like test surface, such as a silicon wafer. The height of a solderball is computed from a simple formula based on the geometry of the specimen and the system configuration. Experimental results demonstrate that the height of a micro-solderball can be readily measured with accuracy in the order of micrometers. © 2004 Society of Photo-Optical Instrumentation Engineers.
Source Title: Optical Engineering
ISSN: 00913286
DOI: 10.1117/1.1668284
Appears in Collections:Staff Publications

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