| dc.description.abstract | As the spacing between components on printed circuit boards decreases, it becomes desirable to mount components in holes of ever decreasing size. Drilling these small holes presents a special problem for the PCB manufacturer. The holes must be made cleanly, with no defects, yet they must be drilled in as little time as possible. Currently, manufacturers adjust their drilling machinery manually, until they are drilling holes with an acceptable rate of rejects. The process of optimizing the drilling operation would be easier if they could predict how adjusting drilling factors would affect the resulting hole quality. In this study the relation between hole quality responses and drilling condition factors was investigated. A series of holes was drilled under different combinations of speed and feed, with temperature and force data recorded for selected holes. The holes were sectioned and photographed with a scanning electron microscope. Quality factors such as smearing, nail heading and void formation were quantized from the photographs. The statistical relationships between the quality responses and the drilling factors was examined. Void formation was inversely proportional to the temperature of the drill bit. The amount of debris found packed into the wall of the holes increased as the chip load increased. Smearing of the innerplanes decreased as chip loads and feed rates increased. Nail heading and burring were proportional to the feed rate. | en |
