LBNL PIXEL IPHC 2009_06_LG1 Flex Cable Development The development of the flex cable for sensor readout and control is envisioned as a 4 stage process that involves the construction of 3 PCB test boards. Since the goal is to have 10 functioning sensors on a ladder for all tests => Probe testing is required for the RDO cable development. Stage 1 - Infrastructure development and testing stage. Test PCB is FR-4 with Cu traces and contains structures that allow for the testing of various sensor infrastructure configurations. This stage is designed to evaluate. LVDS clock multi-drop. JTAG daisy chain. Sensor and system bypass capacitor requirements. Power and ground routing and stiffness. Noise and cross-talk. General operation.

LBNL PIXEL IPHC 2009_06_LG2 Flex Cable Development (cont.) Stage 2 – Production prototype in FR-4 with Cu traces. Stage 3 – Production prototype in kapton with Cu traces. Stage 4 – Production cable in kapton with Al traces. Use what we learn in stage 1 to develop: Making some assumptions about the testing results, We can generate a strawman final cable design with enough detail in the characteristics to evaluate the probable radiation length for Al and Cu conductor versions. Assumptions: 1. Limit the conductor used for power and ground to what is required to give < 50 mV resistive drop for the full power path in the low mass region. 2. The signal list is as we have already defined and multi-drop of LVDS clock and daisy chaining of JTAG works. 3. That what we have learned from the infrastructure testing and later stages does not invalidate any other design choices made here.

3 Flex Cable Development (cont.) Signal# of tracestype Width (0.005 t&s) Sensor output10 x 4 x 2 = 80LVDS (20.32 mm) CLK2LVDS (0.51 mm) CLK_RETURN2LVDS (0.51 mm) Marker1CMOS (0.25 mm) START1CMOS (0.25 mm) SPEAK1CMOS (0.25 mm) JTAG + RSTB5CMOS (1.27 mm) TEMP2analog (0.51 mm) Total (23.88 mm) Number of traces and required width to route (without vias) With 17.5 um Cu trace equivalent thickness. Using industry standard (125um) traces and spaces. Signal 3 LBNL PIXEL IPHC 2009_06_LG

4 Flex Cable Development (cont.) Power traceWidth at thickest part Analog power (5.588 mm) Digital power (2.489 mm) Ground (8.077 mm) Total ( mm) Power Number of traces and required width to route (without vias) With 17.5 um Cu trace equivalent thickness. W = mm 4 LBNL PIXEL IPHC 2009_06_LG

5 Flex Cable Development (cont.) Recall the basic cable geomety We can optimize the conductor layer thickness and the trace size in the low mass region attempting to fit all required conductor into a 2 sided cable, we arrive at the following strawman design. Using standard flex PCB fabrication for the PCB we can use 5 mil spacing and 5 mil traces. We are attempting to fit the routing onto two sides of a mm wide cable or mm. The absolute minimum space required would be ~ = 1.59 (40.4 mm). Designing a layout that fits into the required width for t&s will be very challenging if it is even possible.

Flex Cable Development (cont.) Side view (exaggerated vertical scale) Top View Hybrid Copper / Aluminum conductor flex cable 2 layer Al conductor cable in low mass region (100 um) traces and (100 um) spaces 70% fill factor Conductor thickness in low mass region is 21 um (Cu) or 32 um (Al) Minimum required conductor trace width (33.65 mm) of mm available. Bond wire connection between Al and Cu cable sections. Low mass region calculated X 0 for Cu conductor = % Low mass region calculated X 0 for Al conductor = % 6LBNL PIXEL IPHC 2009_06_LG

7 Flex Cable Development (cont.) Compared to the standard 4 layer Al conductor cable construction; Advantages One 2-layer Al conductor cable – less reliance on Al conductor flex PCB fabrication process and less complex Al structure. Lower radiation length than previous (not as well justified) estimate. More layers and thus more complex structures in the driver region are possible (this may be needed). Disadvantages Wire bonding (or other high density connection technique) required for inter cable connection. Cable will not be the same thickness everywhere – may complicate fixturing. Non homogeneous CTE in cable. 7 LBNL PIXEL IPHC 2009_06_LG