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Tooling and assembly of US stavelet at Berkeley. S. D íez Cornell, C. H. Haber, M. Defferrard , R. Witharm Sept 6th, 2012. Berkeley mechanical meeting, 5th-7th September 2012. Stavelet core.
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Tooling and assembly of US stavelet at Berkeley S. Díez Cornell, C. H. Haber, M. Defferrard, R. Witharm Sept 6th, 2012 Berkeley mechanical meeting, 5th-7th September 2012
Stavelet core • We developed simple tooling for manual assembly and testing of the US stavelet in a quick and easy way • Shield-less tape co-cured in between 0-90 CF layers • Double-sided: DC-DC and serial (serial side shown in the picture) • Al shielding still in one of the modules (honeycomb re-profiled in that region) • Al + polycarbonate inserts to place DC-DC converters (15 mm wide) S. Díez Cornell, Berkeley mechanical meeting
Mechanical tools for manual stavelet assembly • Stavelet frame • Core attached with 2 mm dowel pins • Holes and slots drilled on core plastic inserts • Vertical 5 mm pins on stavelet frame • Module pickup tool + dowel pins • Based on module construction tools • Linear bearings on pickup tool • Modules picked up from module mounting jig by adding removable dowel pins S. Díez Cornell, Berkeley mechanical meeting
Stavelet attachment • Holes and slots drilled on stavelet polycarbonate inserts • 2mm slip fit pins located with set screws on frame • Allows precision placement of core wrt frame S. Díez Cornell, Berkeley mechanical meeting
Pins for module placement • Stavelet is placed on the frame before locating the vertical pins on the frame • Metrology measurements determine the location of HV reference pads on the bus tape with respect to the stavelet frame • Pickup tool is referenced wrt those reference pads • Location of vertical pins is then determined • Allows re-positioning of the core anytime knowing the location of the reference pads S. Díez Cornell, Berkeley mechanical meeting
Module gluing • Silver epoxy : • HV contacts to sensor backplane • Two contacts (as opposed to previous stavelets) • Three layers of low tack (blue tape) mask for SE4445 • Very similar to the one used at RAL Additional Kapton tape layer to avoid electrical contact between HV backplane and CF shielding • Fishing lines : • 150 μm diameter • Height control • Allow to remove the SE4445 (but probably not the silver epoxy...) S. Díez Cornell, Berkeley mechanical meeting
Module placement • Module is vacuumed down on the ASICs and picked up from the module construction jig • The module is picked up with sensor-ASIC wire bonds (PUT gives 500 μm clearance) • Removable dowel pins keep the pickup tool in place • Linear bearings on the pickup tool fit the vertical pins on the frame • Fishing line controls glue thickness, it could also be done with washer shims on the pins S. Díez Cornell, Berkeley mechanical meeting
Glue trials 2 layers mask: ~160 μm of glue No glue spreading at all 3 layers mask: ~ 240 μm of glue (may need to change mask layout) S. Díez Cornell, Berkeley mechanical meeting
Other components • EoS and BCC boards attached with double sticky tape • DC-DC power: • Power bus tape (+1Wire lines) modification required due to higher current (~ 10 A) with respect to serial powering (~ 5A) • Converters go on top of the tape, there is a significant step (~ 550 μm) wrt the lateral inserts that prevents thermal contact between converters and Al inserts • Step is even higher on the Al shielded module since the inserts were trimmed (~750 μm) • AlN ceramic pieces glued down the inserts and the converters backplane with FH-5313 epolite to overcome the step and to get good thermal contact • EoS board doesn’t stand 10 A either • >10A rated wires soldered directly on tape S. Díez Cornell, Berkeley mechanical meeting
US Stavelet so far • Started with DC-DC side, 3 out of 4 modules placed S. Díez Cornell, Berkeley mechanical meeting
Position of modules with respect to tape Δx Distance (mm) Δy Module 0 Module 1 Module 2 (Al shield) • 2 points per module on the power side • Δx = 1009 ± 146 μm • Δy = 565 ± 72 μm Module 2 (Al shield) Module 0 Module 1 S. Díez Cornell, Berkeley mechanical meeting
Modules relative position • Target values and clearance: Δx = 500 μm, Δy = 0 • Average glue thickness ~ 175 μm for all 3 modules 453 μm 441 μm 322 μm 484 μm 170 μm 47 μm Module 2 (Al shielding) Module 0 Module 1 S. Díez Cornell, Berkeley mechanical meeting
Stavelet electrical performances • 3 DC-DC modules mounted so far • Module 0 was badly damaged during its removal from its individual test frame • Last step in the process before placement on core, only one that didn’t involve test (now it does) • “Good” news is that now we can study module removal techniques… S. Díez Cornell, Berkeley mechanical meeting
I-V curves modules 1 and 2 • IV curves during operation (cooled down, N2, LV power on) • FZ2 series II sensors (higher currents than FZ1 series) • Roughly an extra μA with respect to individual on both cases Module 1 Module 2 (Al shielding) S. Díez Cornell, Berkeley mechanical meeting
ENC noise modules 1 and 2 • Very fresh results (very first measurement of stavelet with 3 (2) modules) • ENC noise on module 1 is reduced by ~ 40-50 e just by placing module 2 • Excellent ENC noise results for module 1 Module 1 Module 2 (Al shielding) 646e 639e 663e 663e 633e 633e 601e 611e S. Díez Cornell, Berkeley mechanical meeting
Hybrid to hybrid reference path • Low inductance connection required between GNDs of both hybrids of each module • Usual bus tape connects them through Al shielding • That is why the Cu squares are for in our tape • Problem: the (shortest path) pad for one of the hybrids is covered by the sensor • Comes from the tape layout, not the module placement • Have to perform some surgery to achieve low inductance connection • Reduced noise of left hybrids by > 50e S. Díez Cornell, Berkeley mechanical meeting
NTCs and Sensirion humidity sensors • Data taken by sctdaq right after 3PointGain test • TChiller = 9 C • Test box flooded with N2 21.5C 23.4C 21.5C 21.4C 23.8C 22.0C 15.0C 4.5%RH 19.1C 3.4%RH S. Díez Cornell, Berkeley mechanical meeting
Lessons learned • The tools allow placement of the modules on the stavelet with a precision of ~150 μm • At a very first glance, and comparing with UK DC-DC stavelet, CF shielding works electrically as well as Al shielding • Al shielded module shows no particular advantage electrically wrt CF module • NTC measurements show uniform thermal behavior of all 3 modules • Pickup tool propagates quite some errors (location of module on pickup jig, hybrid gluing, cable deformation, location of bearing pins,…) • It would be better to have more control on the Z dimension, and also making the frame compatible with WB equipment • Still work in progress; will be interesting to see how serial side comes out S. Díez Cornell, Berkeley mechanical meeting
Future • Removal and replacement of defective module • Last DC-DC module and serial powering side to be populated in the following weeks • Modules already in hand (built at Santa Cruz) • Extensive electrical measurements foreseen in the near future • Second US stavelet (SP, single-sided) for BNL/Penn to be assembled with these tools • US-type core with CF side pipes • Have to look for different attachment pins (“V-shaped” pins) S. Díez Cornell, Berkeley mechanical meeting