Heuser, J.

Schmidt, C. J.

Soyk, D.

Tymchuk, I.

GSI Repository

Silicon strip sensor layout for CBM STS ∗D.Soyk†1, I.Tymchuk2, J.Heuser1, C.J.Schmidt1, for the CBM collaboration1, and the FAIR@GSIRBDL11GSI, Darmstadt, Germany; 2LTU, Kharkov, UkraineThe CBM Silicon Tracking System will be equippedwith double-sided Silicon micros-strip sensors, where thestrips on the p-side are inclined by 7.5◦ with respect tothe n-side strips as well as the sensor edge. The final andhomogeneous layouts for the 3 different sensor lengths,namely 22mm, 42mm and 62mm, has been elaborated.Longer sensors may be realized as a daisy-chain of two62mm sensors. The sensors will be produced by two ven-dors to avoid the stop of module production in case of prob-lems with any one single vendor.The stereo angle of 7,5◦ effects a correlation between thex and y coordinate of a bond pad on a strip. The x distancebetween to strips on the sensor is 58µm, equivalent to thepitch of the straight n-side strips. Therefore the second rowof bond pads must have a y distance of at least once themultiple of 58µm/tan(7,5◦). On the sensor a pad patternwith x distance of 58µm and y distance of ∼440,554µmis possible, but the minimum producible pitch for the longanalog microcables is in x direction 116µm. In order tocontact all strips, a double layered cable needs to be em-ployed und thus a doubly staggered bond pattern is needed.This leads to a checker-board-pattern where every sec-ond pattern-point is alternatingly reserved for a bond pad.The pitch of the bond pads is in x 116µm and in y ∼881.108µm (the center of the pads in the second row isshifted in x direction by 58µm relative to the center of thefirst row of pads). Figure 1 shows an exemple of the suchpattern.Figure 1: Schematic view on the bond pad and DC padpattern.As there are different lengths of sensors and as the padrows should be located on the same x-position on the topedge as on the bottom edge it proved most adequate to al-locate the origin of the coordinate system in the center ofthe sensor. Further, the distance from the coordinate cen-ter to the innermost pad row was fixed to be a multiple of∗Work supported by FAIR@GSI PSP code: 1.1.1.2.1.1.† d.soyk@gsi.dethe y-pitch of two staggered pad rows, namely 881.108µm. Consequently the distance from the outermost pad row tothe edge of the sensor is a variable of the sensor length, asthe pre-chosen lengths are none multiples of this pitch.Figure 2: Schematic view of a sensor to sensor daisy chain.The red and blue lines are the leads of the short 58µm-pitchcable that serves to daisy chain two sensors.These definitions together with the respective symme-try allow daisy-chaining of sensors of the same as well asdifferent lengths to each other. Figure 2 shows two daisy-chained sensors with a microcable of a constant lead length.Consequently, also one FEB-design may serve all sensorconfigurations as well as either sensor side. In figure 3 ascheme of a microcable connection between the foreseenCBM STSxyter chip and the STS sensor is shown.Figure 3: Schematic view of a sensor to chip connection.The red and blue lines are the leads of the microcable ontwo different layers with a pitch of 116µm.All participating vendors will employ this layout of thebond pads even though they may vary the sensor designaccording to their proprietory design and production pref-erences.GSI SCIENTIFIC REPORT 2013 FG-S-FRS-03doi:10.15120/GR-2014-1-FG-S-FRS-03 335

Silicon strip sensor layout for CBM STS

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Silicon strip sensor layout for CBM STS

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