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

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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)

Stavelet core

6th Sept 2012

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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

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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

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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

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Module gluing

6th Sept 2012

Silver epoxy :● HV contacts to sensor backplane● Two contacts (as opposed to previous stavelets)

Fishing lines :● 150 μm diameter● Height control● Allow to remove the SE4445 (but probably not the silver epoxy...)

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

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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

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Glue trials

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2 layers mask: ~160 μm of glueNo glue spreading at all

3 layers mask: ~ 240 μm of glue(may need to change mask layout)

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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

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US Stavelet so far

Started with DC-DC side, 3 out of 4 modules placed

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Position of modules with respect to tape

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0.4

0.5

0.6

0.7

0.8

0.9

1

1.1

1.2

1.3

0 1 2 3 4 5 6 7

Δx (mm)Δy (mm)

Δx

Δy

Dis

tanc

e (m

m)

Module 0 Module 1 Module 2 (Al shield)

Module 0 Module 1 Module 2 (Al shield)

2 points per module on the power side Δx = 1009 ± 146 μm Δy = 565 ± 72 μm

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Target values and clearance: Δx = 500 μm, Δy = 0

Average glue thickness ~ 175 μm for all 3 modules

Modules relative position

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Module 1Module 0 Module 2(Al shielding)

322 μm47 μm

441 μm

484 μm170 μm

453 μm

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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…

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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

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Module 1 Module 2 (Al shielding)

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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

ENC noise modules 1 and 2

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646e

663e

633e

611e

Module 1 Module 2 (Al shielding)

639e

663e

633e

601e

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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

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NTCs and Sensirion humidity sensors

Data taken by sctdaq right after 3PointGain test TChiller = 9 C Test box flooded with N2

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21.5C 23.4C 21.5C 21.4C 23.8C 22.0C

19.1C3.4%RH

15.0C4.5%RH

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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

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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)

6th Sept 2012