Optimization of AOI processes

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Janóczki Mihály
Department of Electronics Technology


I’ve been taking place in a new project of a famous automotive supplier as

process engineer. Our department is responsible for the assembly processes. The

products must work reliably in extreme environmental conditions, therefore certain

components need special protection.

The solder bumps of BGA (Ball Grid Array) package provide mechanical fixing

and electrical contact with the PCB (printed circuit board). Electrically insulating glue is

dispensed under the package (with a so called underfill technology) in order to shield

the bumps from harmful effects and to enhance the strength of the fixing.

The automatic optical inspection (AOI) provides the only one in-line underfill

inspection opportunity. My task was to develop the inspection process, since the

installed AOI equipment frequently signs pseudo errors. The reason of this malfunction

is that the quality of the picture made by the optical head unit is not sufficient for

reliable image processing.

In this document I’ve presented several underfill technologies and their quality

inspection methods. I’ve described the optical inspection technologies and the

illumination systems.

I’ve found out the problems of the current illumination system and developed an

efficient lighting for the glue inspection process. I have simulated lightings with several

wavelengths and made comparative measurements with Matlab Image Processing

Toolbox software. After the tests I’ve described the feasible solutions. I’ve selected the

best resolutions considering the measurement results and the company’s needs. At the

end I’ve evaluated the developed solution and aimed the attention to the bottlenecks as



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