Investigation of innovative silicon detector assembling solutions for hadron calorimeter modules

The application of large areas of silicon detector mosaics in calorimetry for high energy particles measurement in Physics has grown in the last few years and is still in progress. The high number of mosaic units in the calorimeter implies the following main requirements to be satisfied: a simple low cost for manufacturing and assembling, easy mountable/dismountable units, possibility to move or change silicon detectors easily, reliability of the electrical contacts between the aluminium layer on the silicon detector surface and the PCB breaker points.In order to satisfy the above requirements several assembling solutions have been investigated and tested recently, as fixed contact by using conducting epoxy-glues, mechanically dismountable contacts of gold-plated PCB copper to the silicon detectors, and others.The results of the tests show a general degradation of the original electrical characteristics of the contacts after of varying lengths operating times.This fact, due to corrosion phenomena assisted by chemical residuals in the contact interface, causes an irreversible damage of the detectors in the long term.In addition we found a room temperature interdiffusion of gold and copper.A promising solution to these problems can be achieved by careful removal of chemical, increase of golden layer of the PCB electrical copper contacts or aluminising them by pure aluminium vapour deposition in vacuum chamber.Thee estimated degradation time between the PCB copper and the aluminium film is very low in this case, and the risk of diffusion in the detector aluminium film surface is low along the whole operating life of the calorimeter. (orig.)