HYBRIDS- construction

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HYBRIDS- construction
SUBSTRATES
CONSTRUCTION of composite SUBSTRATE - many
lay-ups tried best flatness obtained
with TPG central core 400um woven layer of CF
prepreg each side oriented -45 degrees 125um
nominal woven layer of CF prepreg each side
oriented 0,90 degrees 125um nominal Laminated in
vacuum press at Stevenage Circuits Total
thickness 900um very flat - float when
dropped on flat surface both sides thickness
variation -30um at edges from epoxy
extrusion Frame of Carbon Fibre 3mm wide
introduced to prevent delamination at the edges
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HYBRIDS- construction
SUBSTRATES 2
CONSTRUCTION of composite SUBSTRATE Frame of CF
3mm wide introduced to prevent de-lamination at
the edges CF and TPG outlines shown in RED the
substrate is routed from the kit of these parts
to the substrate profile shown in GREEN the
circuit is shown in BLUE
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HYBRIDS-construction
CIRCUITS

• Four copper layers with Kapton dielectrics bonded
  with 35um Espanex (modified polyimide) bondply
  essentially a standard multilayer flexi circuit.
• DESIGN RULES - not very tight for the technology
  ? good yield
• 100um track and gap
• 300um vias - 500um lands no buried vias
• Layer material pressed copper thickness
• thickness top bottom
• solder resist 30
• copper foil 05carrier 5um 5um -------
• SPB-050A Bond Ply 50um (was 35) -- --
• 2/3 SB1250 Cop/Clad flexi 60um 12um 12um
• 12/50/12 (Adhesiveless) (power)
• SPB-050A Bond Ply 50um (was 35) -- --
• 4 copper foil 05carrier 5um -- 5um
• total 200um (ground)
• NB plating thickness of 8um Cu is added to
  top and bottom Ni/Au on top

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HYBRIDS- construction
CIRCUITS layout
Component and trace layout
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HYBRIDS-construction
Lamination to form a HYBRID
Two CIRCUITS are now bonded back to back on the
SUBSTRATES using the corner holes for alignment.
The cut-outs in the corners allow for the
differential expansion of the jig relative to the
circuit and avoid stressing of the substrate when
heated. Bonded using 50um bond Ply as in the
circuit construction Total thickness 900um
(substrate) 2 50um (bondply)
2200um(circuits) 1.4mm Note K4s have had
PA dowel and central tooling holes holes drilled
in the substrate and circuit separately before
lamination. For K5s, if Pitch Adapters are not
to be fixed at the same time as the circuits are
laminated, a third drilling step will drill
these holes after lamination to give a cleaner
finish.
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HYBRIDS-construction
Pitch Adapters
Pitch Adapter designs for Phi and R - need new
fiducials for production. All locations are
different, drawn in sets of 4
One complete set of Phi and R on one sheet 20
sets delivered today Ni/Au on Cu 22um min TG
Rfanout detector end
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Pitch adapters tested at Liverpool will be
shipped to Stevenage circuits as kits of 8
pieces for lamination to hybrids in vacuum press.
(to avoid air entrapment) Stevenage have
confirmed they are willing to develop this.
Details of jigging to be confirmed.
Method Bottom jig plate has pins loosely held
(avoiding CTE mismatch stress) to match holes in
bond-ply segments( DARK BROWN), PA
segments(LIGHT BROWN) and hybrid (LIGHT
BROWN AND BLUE) Packing pieces (GREEN) keep the
assembly planar. Protection pad (RED) is shown
with a cut-out but will have only holes for the
pins Top jig plate (NOT SHOWN) would have loose
holes for pins It is in principle possible
to do this operation at the same time as the
lamination of the circuits to the substrate.
HYBRIDS-construction
Pitch adapter attachment
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CIRCUITS fanouts detectors
HYBRIDS- construction

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HYBRIDS
Population
Tests on early prototypes showed that reflow
soldering would produce distortions as the whole
hybrid would be heated beyond the glass
transition temperature of the adhesives without
the hybrid being supported. It was therefore
decided to Hand solder the components. Bond
areas (and P.A.s when they are fitted) are masked
to prevent solder splashes and damage. Three
companies have quoted for this work. One (Hawk
Electronics, Accrington UK) has populated 2.5
hybrids (no fanouts fitted) with good (visual)
results. All three companies use a water
removable flux and circuits are washed with a
water based solvent and air dried at low
temperature. First hybrids returned are not clean
to the standard needed (some flux residues can be
seen) and will be cleaned with Prozone, a solvent
based PCB cleaner on return to Liverpool. (this
has been used on the previous modules with good
results).
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HYBRID- construction
Detailed sequence 1
Hybrid construction sequence   Liverpool 1.1)
TPG and CF Kits prepared and sent to Stevenage
circuits 1.2) Sets (8 pieces) of tested Pitch
Adapters (PAs) sent to Stevenage   Stevenage
2.1) TPG and CF kits laminated in vacuum press
to form substrate   2.2) Substrate profiled,
drilled and routed (note 1)   2.3) Four layer
kapton circuits produced, 2 per module 2.4)
Circuits electrically tested before and after
Ni/Au process   2.5) Circuits laminated to each
side of substrate in vacuum press to produce
hybrid   2.6) Mark one side of hybrid with
sequence number in Red R side   2.7) Post
lamination electrical test of hybrid (if
possible - note 2)   2.8) R and Phi PAs
attached to hybrids in vacuum press   2.9)
Completed hybrids sent to Liverpool  
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HYBRID- construction
Detailed sequence 2
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HYBRIDS testing (K4)
HT TEST
Hybrid short cable tested together in Vac
Tank Hybrid populated with decoupling caps
(2500v 10nf to Gnd) Guard and HT shorted
together All lines except HT and Guard on HT
connector shorted to ground (includes
Power) Discharges (brief up to 15nA ) seen on
ramping up above 430V 0.4nA leakage at 500V for 1
hour 0.2nA leakage at 500V if taken to 510 and
back down again. ? holds 500V but need more
statistics K5 clearances are the same as K4 so
no differences expected
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HYBRIDS testing (K4)
Performance

• Three single sided modules have been successfully
  operated in November test beam.
• No functional problems encountered with powering,
  configuring and reading out.
• But there is readout pulse shape distortion
  caused by
• thickness constraint on modules and possibly
  cable geometry ( impedance mismatches)
• Thin dielectrics on the hybrid ? high (25pF)
  capacitance on 100mm of hybrid trace which loads
  the output drivers.
• Impossible to obtain transmission line
  performance over the short (100mm) trace length
  on the hybrid (drivers see a reactive rather than
  resistive load). This is essentially a fixed
  parameter constrained by dielectric thickness)
• On exiting the hybrid the analog signals travel
  over a 300mm length through the short tails and
  then through the Nikhef long tails.
• Simulations of the readout chain have been done
  by Jan Buytaert and we await these results before
  proceeding with cable fabrication.

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HYBRIDS K4?K5
Changes
Numbered chips (0-F) for simpler reference when
scanning under scope Put copper in corner tab
area to stiffen it More and larger chip
fiducials new F shapes orthogonal to bonder
axes. New circular Fiducials for population
  Placement markers removed from under detector
guard rails  Split power plane into four and
added decoupling caps between sections Add 3 new
sense lines resistors (0 ohms in 0V 100 ohms in
power)  Moved caps at side of chips for bonding
side bonds  Removed HT leak resistors  Made HT
filter resistors 0805s (100volt rating) or
1206(200V rating) HT caps return to ground not
HT ret  Moved components HT inwards  Power on
reset to uses old DAV pair 50 ohms to GND on
return side of the pair.  Two semitek temp
sensors at bottom and RHS  RAD monitor pads
provided at centre of RHS Move resistors next to
connectors to allow removal tool to be used PAs
----- areas still neededfor bonding off  Fanout
------ fids are not regular and end up underneath
bonds.   Fanouts need larger fids Fanout ------
consult Mark Mike on best fid design