Tooling and assembly of US stavelet at Berkeley

1. 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

2. 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

3. 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

4. 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

5. 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

6. 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

7. 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

8. 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

9. 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

10. US Stavelet so far • Started with DC-DC side, 3 out of 4 modules placed S. Díez Cornell, Berkeley mechanical meeting

11. 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

12. 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

13. 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

14. 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

15. 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

16. 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

17. 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

18. 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

19. 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