| 摘要 |
A procelain on steel printed circuit board includes apertures whose edges are rounded. An aperture is formed by first punching or otherwise making an aperture in the uncoated steel of somewhat larger size than desired, then employing a pair of dies, each with rounded shoulders and a center region of smaller area than the aperture. When the board is placed between the dies with the center region of the latter aligned with an aperture, and pressure is applied to the dies, they engage and round the edges of the aperture. The excess displaced material is forced into space between the original peripheral edge of the aperture and the center region of the dies, thereby decreasing the size of the aperture to the desired size and forming a relatively smooth tapered transition region between opposite surfaces of the board and the outer circumference of the aperture of reduced size. The steel is coated with porcelain after the finished apertures are formed. |
