a low - cost , high - performance , reliable micromirror package that replaces the ceramic substrate in conventional packages with a printed circuit board substrate and a molded plastic case , and the cover glass with a window , preferably an optically clear plastic window . the printed circuit board substrate allows for either external bond pads or flex cable connection of the micromirror package to the projector &# 39 ; s motherboard . these packages support flexible snap - in , screw - in , ultrasonic plastic welding , or adhesive welding processes to overcome the high cost seam welding process of many conventional packages .