Ultra-thin, high-precision flex cable for the L3 silicon microvertex detector

We describe an ultra-thin, high-precision Kapton flex cable for use as a signal router in the L3 Silicon Microvertex Detector. The excellent mechanical and electrical properties of this cable make it dimensionally stable against temperature and humidity changes, as well as maintaining cross talk below 3% between adjacent lines. Electron beam photolithography and chemical etching technology have produced a cable with typically 11 μm wide lines spanning continuous lengths up to 14 cm, with sufficient alignment accuracy to match both input and output pads over the entire length of the detector. Electroplated input and output pads allow automated wire bonding with excellent pull strength and high efficiency. (orig.)