Height Measurement of Micro-Solder Balls on Metal Pad by White Light Projection

Micro-solder balls are commonly used in wafer-level ball grid array (BGA) packages as an interconnection medium. To measure the height of a micro-solder ball on a metal pad, we propose a white light projection method to avoid interference from pads in the shadow of the ball. The optical projection o...

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Bibliographic Details
Published in:IEEE transactions on components, packaging, and manufacturing technology (2011) packaging, and manufacturing technology (2011), 2012-09, Vol.2 (9), p.1545-1549
Main Authors: Wang, Fuliang, Qin, Jingwen, Han, Lei, Wang, Hengsheng
Format: Article
Language:English
Subjects:
Applied sciences
Arrays
Ball grid array (BGA) package
BGA
Design. Technologies. Operation analysis. Testing
Educational institutions
Electronics
Exact sciences and technology
Fundamental areas of phenomenology (including applications)
height measurement
Illumination
Inspection
Integrated circuits
Light emitting diodes
Measurement by laser beam
Metals
micro-solder ball
Optical imaging
Optical sources and standards
Optical variables measurement
Optics
Optoelectronic devices
Physics
Projection
projection method
Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices
shadow image
Shadows
Solders
Substrates
White light
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Summary:Micro-solder balls are commonly used in wafer-level ball grid array (BGA) packages as an interconnection medium. To measure the height of a micro-solder ball on a metal pad, we propose a white light projection method to avoid interference from pads in the shadow of the ball. The optical projection of a solder ball under the illumination of a parallel white light beam is studied, and the relationships between the ball height, ball radius, and shadow length are deduced. An experimental platform with a simple optical system and white light emitting diodes lighting source is constructed to obtain ball and shadow images, and a program developed to process these images and calculate the ball height. The heights of the balls on a BGA chip are measured using this new method, and the results verified using a commercial optical profiler. This method is not sensitive to the patterns on the substrate surface and has great potential for future application.
ISSN:2156-3950
2156-3985
DOI:10.1109/TCPMT.2012.2193617