The improved ladder production for the Belle silicon vertex detector (SVD2.1)

In autumn 2003, data taking with the new silicon vertex detector SVD2.0 in Belle started at the KEK-B energy-asymmetric e/sup +/e/sup -/ collider in Tsukuba, Japan. The detector works as expected, however, it was decided to produce replacement ladders for the inner two layers of the vertex detector which are most exposed to the high radiation dose from the beam. The new ladders do not merely reproduce the existing design but include some significant improvements. The readout electronics is implemented on a hybrid board with a new heat transfer scheme in order to dissipate the heat produced in the front-end readout chip. The flex circuits that connect the double-sided silicon sensors (DSSDs) with the hybrid boards were redesigned using a 2-layer technique which improved the production quality and lowered their costs significantly. Production and testing will be finished in summer 2005 and will provide Belle with spare ladders as well as new expertise for possible future projects for example the high luminosity B-factory.