Minutes of the GTK carrier Design Review meeting The meeting has been held on Wednesday, April 29th at 14:00. The discussion has been lead by Michel M., who presented the slides reporting all the changes implemented in the second version of the GTK carrier prototype. Slides are archived in http://indico.cern.ch/event/389362/contribution/0/material/slides/0.pptx Most of the discussion has been devoted to the wire-bonding of the detector and PCB. The complexity of the card and in general of the interconnection is such that an optimal solution is almost impossible to be implemented and we have now to find a good compromise.

Two solutions have been proposed by Michel named in short: Thinner countersink Stairway to bonding area (please, look at the Michel’s presentation slides 4 and 10 forthe sketches) After a long and fruitful discussion it was clear that the best solution was somewhere a mix of the two. The arguments were the followings: With the Thinner countersink, the PCB would have been 560 mm thick and appears to be mechanically too weak. Such solution would have required a further frame to stiffen the structure (a stiffener). The stiffener should work on all the contour area and replace the elastometer, which is applied only on three spots. However the changes required to install a stiffener do not seem to be easy, together with a new procedure for the assembly. A similar problem should be faced with the solution Stairway to bonding area. The addition of a stiffener would require a flat surface of the PCB, which is not easy to obtain.

Apply a single step for the ground pads. The solution, which appeared to be a good comprimise, was the following: Let the countersink to be 800 mm thick, in such a way that is sufficiently stiff. Apply a single step for the ground pads. Increase the distance between detector pads and PCB pads from 1 to 1.5 mm. Sig1 Sig2 VDD VDDA GND 800µm Countersink area 14.5mm 1.5 mm PCB Micro-cooling plate sensor TDCpix Frame