For BGA inspection, it is my feeling that he most effective technique a facility can use is the combination of a transmission x-ray system in conjunction with an endoscope (side viewing optical microscope). In using the transmission x-ray inspection system, what one is looking for for rapid qulification of solder bond integrity, is unifomity in shape and size of the ball bonds. If the x-ray image of the balls appear uniformly round and equal in size, the probability is exteremly high that the whole reflow process is under control. Any deviation from uniformity (signature)has a particular interpretation and the endoscopic confirmation is then in order.Examples of some signatures can be found in IPC-7095. In terms of safety, every facility should have a radiation safety program in place. This should include the use of dosimeter badges, radiations survey meters and operator instruction. You can find moreradiation safety information on: http://www.glenbrooktech.com
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