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Optical Engineering

Inspection of micro-solderballs on a semiconductor bumped wafer using optical shadowgraph
Author(s): Cho Jui Tay; Shi Hua Wang; Chenggen Quan
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Paper 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.

Paper Details

Date Published: 1 April 2004
PDF: 8 pages
Opt. Eng. 43(4) doi: 10.1117/1.1668284
Published in: Optical Engineering Volume 43, Issue 4
Show Author Affiliations
Cho Jui Tay, National Univ. of Singapore (Singapore)
Shi Hua Wang, National Univ of Singapore (Singapore)
Chenggen Quan, National Univ. of Singapore (Singapore)

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