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Optical techniques have been a key ingredient in greatly improving the quality control and product assurance of solar panel manufacturing. In fact, major breakthroughs in this area have been in progress over the last two years. These techniques involve electro-optical devices used for on line sensing and, in some cases, controlling production. Optical sensor displays assist the operator and inspector to assure maximum quality control. The sensors output is simultaneously, along with other pertinent data, recorded for documentation and stored for future reference. In this age of very large, lightweight, folding solar arrays, the individual solar cell bonding to the circuit is most critical. The bond must be strong mechanically, good electrically and introduce no undesirable side effects such as puncturing the junction, cracking the cell, or melting the circuit material. One related problem is mislocating the bond such that edge effects or unwanted insulation material interfere with the bonding, reducing the strength and size of the bond. This alignment problem was solved by using a high resolution, high contrast color TV camera with high contrast capability allowed detection of the low contrast insulation material. Color effects immediately after bonding, giving the inspector, bond quality and bond shape data, as well as revealing any circuit melting. Since bonding takes only a few milliseconds and there can be more than 20 variables involved, a sensor controlled bonder was required. This was solved by means of an electro-optical bond temperature sensor that automatically controlled the bonder to a preset bond temperature. Another inspection technique utilized was an electro-optical sensor which consisted of a custom designed videoized near infrared microscope that permitted crack inspection after bonding and gives infrared bond footprints. By inserting crossed polarizers, inspection of the residual stress patterns left in the silicon was possible. In addition, a robotic solar cell bubble inspection concept is also presented in the last part of this paper.
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