Abstract: A composite stencil for screen printing solder paste includes a layer of metalic material such as brass and a layer of flexible material bonded to the metalic layer. The metalic layer has a thickness of 0.002 to 0.010 inches, while the flexible layer is 0.002 to 0.010 inches thick. The combined thickness of the composite stencil is approximately 0.008 to 0.012 inches. The stencil can be manufactured by forming openings in the metalic sheet and then applying a layer of photosensitive flexible material to the metalic sheet. The metalic sheet is then used as a stencil to expose the photosensitive material.

Abstract: A drilling system and method for use on thin frangible workpieces, such as watch crystals and the like, in which the speed of rotation and pecking motion of the drill are programmed to execute a preset schedule of changes with minimal human intervention.In a preferred embodiment, the drill is mounted over the workpiece, which is pneumatically clamped on the work surface in a shallow water bath. The vertical pecking motion of the drill is under the dual control of a primary cable tensioned by weights on one end under control of a solenoid; and a secondary cable, the tension of which is responsive to the rotation of a master cam. The latter also initiates relay action for sequential operation of controls. The drill operates at an initial, relatively low rotational speed and a brisk pecking motion. At a preselected point near the lower end of the drill hole, the rotational speed of the drill is shifted to "high", and the pecking motion is slowed.