mikhail kubantsev - kansas state university 1 assembly of a large area microstrip silicon tracker...

Mikhail Kubantsev - Kansas State University

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Assembly of a Large Area

Microstrip Silicon Tracker

Assembly of a Large Area

Microstrip Silicon Tracker

Some Experience of Construction of D0 SMT

H-disk Silicon Detectors March 16 2000


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OutlineOutline

Introduction: Overall Design Detectors Mechanical Tolerances Electronics Thermal Conditions

Mechanical assembly of modules (half wedges)

Testing and diagnostics of modules

Construction of full wedges and disks

Perspectives and conclusion


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Experiment D0 Experiment D0

Silicon MicrostripTracker

Scintillating fiber tracker


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SMT made of Barrels and Disks

Ladders make up Barrels

Wedges make up Disks

SMT made of Barrels and Disks

Ladders make up Barrels

Wedges make up Disks

F-DISKS

H-DISKS

BARRELS


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Silicon SensorsSilicon Sensors

Double and single sided detectors for barrels Double sided for F-disks Single sided for H-disks glued back to back Total of 147,000 readout channels on 1.26

square meters of silicon detectors are to be assembled as H-disks


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SMT ReadoutSMT Readout

Basic element is a SVX-IIE chip with 128 channels of 8-bit ADC, sparsification, , buffers, and output drivers

The SVX chips are installed on the High Density Interconnect (HDI) flex circuit laminated on the berullium substrate

Digital information is passed to readout sequencers and via optical links to VRB’s and to computers


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Temperature Control

Temperature Control

The readout generate a substantial amount of heat ( about 3.8 watts/HDI) or 185 watts for one H-disk

The cooling channels made of beryllium will support the structure and provide cooling

Temperature of silicon detectors should be close to 0oC so they have to be in dry atmosphere (nitrogen gas)

Mixture of water and ethylene glycol is used as a coolant at temperature of -10oC


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Track Measurements

by H-disks

Track Measurements

by H-disks H-disk subsystem is a tracking device

and not a vertex detector measuring tracks in rapidity interval 2.2 -3.0. Particle momentum is measured in r- plane (magnetic field is normal to the disk) .

Detector position accuracy of 10 - 15 is expected

The track momentum is measured by combination of barrel ladders (vertex position), F-disks and H-disks.


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H-disk TolerancesH-disk Tolerances

Numerical estimations and detailed Monte-Carlo studies showed that tolerances in r- plane should be better then 25 and few hundreds along the beam direction.

Intrinsic H-disk precision:


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Structure of the H-diskStructure of the H-disk

H-disk shroud

Beryllium cooling channel

Scintillating fiber tracker

barrel

24 wedges installed on the cooling channel


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Half Wedge -Basic Module of

the H-disk

Half Wedge -Basic Module of

the H-disk

Outer silicon sensor

(under Be substrateand HDI)

Inner silicon sensor

Be substrate

HDI

65 cm2 areaof silicon


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H-disk Production Team

H-disk Production Team

Kansas State - Moscow State - Fermilab team: M.Kubantsev(team leader) KSU E.Shabalina MoSU M.Merkin MoSU D.Karmanov MoSU G.Derylo Fermilab G.Sellberg Fermilab S.Jakubovski Fermilab N.Ronzhina Fermilab


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H-disk Design and Production Philosophy

H-disk Design and Production Philosophy

Vigilance on production since silicon is not permissive: clean room environment

With alignment at when two half wedges are stuck together

With alignment at when 24 wedges are put on the large cooling ring

Puts problems:

- Use single-sided sensors- Define required precision of assembly.- Develop assembly procedures - Make a pre-production batch of modules- Full scale production of modules- Make two half wedges and stick them together -Put 24 wedges on the cooling ring with high precision


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Major Production

Steps

Major Production

Steps Obtain and test sensors HDI fabrication: flex by

Compunetics,lamination by Fermilab, stuffing by Promex/Silitronics, testing by CSUF/KSU/KU/Fermilab

Here is our starting point:

silicon, beryllium,flex circuit


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Major Production Steps

(Continue)

Major Production Steps

(Continue) Half wedge assembly Half wedge testing Full wedge assembly Ring Assembly Wedges mounted on Rings Over test of the rings Installation and commission at

the D0 detector


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H-disk Si SensorsH-disk Si Sensors

H-Wedges have inner and outer sensors that are made by ELMA(Russian) and Moscow State University with 4” technology.

Silicon detectors have 40 pitch, 80 readout pitch

About 500 are here, tested and more than a half assembled in the (half)wedges but we will need 60 detectors more to be delivered late spring.

Outer silicon detector control measurement on the coordinate measuring machine


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HDI-Beryllium Lamination

HDI-Beryllium Lamination

Set up 2 sandwiches of parts on the special fixture: the bare HDI, epoxy glue film, Be substrate, conductive

epoxy glue


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Lamination (continue) Lamination (continue)

Put the sandwiches in the oven and bake them with a special compressed air press (shown below) using accurately determined temperature and pressure cycles (it took two months to determine it!)

Can make 4 HDI laminations per day


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HDI Stuffing HDI Stuffing

Insufficient parts throughput

Bubbling in surface mount stage at Promex

Wire bonding pull strength problems

Low efficiency of production

Find more then one vendor

Bake out to remove moisture from kapton

Plasma cleaning after parts surface mount

Work with company on testing

Problem Resolution

Product - a stuffed HDI:Present yield - 80%


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Module - Half Wedge Assembly

Module - Half Wedge Assembly

The fully tested HDI on Be substrate is glued with an outer silicon sensor and a supporting beryllium plate

3M adhesive film is used to reduce mechanical stress on silicon to speed up production from 24 hours to 2-3 hours to make one glue joint

Working on gluing procedure


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Assembly of Half Wedge

(Continue)

Assembly of Half Wedge

(Continue) The assembly is made on precision

fixtures with accuracy of 50 The inner detector is attached to

the outer detector with high accuracy 2-5 with special fixture using CMM OMIS.


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Wire Bonding of the Half WedgesWire Bonding of the Half Wedges

Wire bonding on the hybrid flex circuits is made by vendors (Promex, Silitronics)

Bonding of the SVX chips to pitch adapter,pitch adapter to outer detector and outer to inner detector is made on high speed bonding machines 8090.

Over 2000 bonds per half wedge are made in less than 30 minutes

SVX chip wire bonding to the flex circuit


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Encapsulation of Wire Bonds

Encapsulation of Wire Bonds

Encapsulation of wire bonds on the fully tested half wedges is made

with the computer controlled motorized table watched by two

TV cameras .


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Encapsulation (continue)

Encapsulation (continue)

Special combination of 2 materials with different viscosity is used to encapsulate dense wire bonds on the detector-pitch adapter connection.

Encapsulation is cured with ultra violet

light lamp

TV image of encapsulation process:

top and side(insert) views


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HDI/Wedge Testing:

Functional Test

HDI/Wedge Testing:

Functional Test HDI and Wedge/Ladder functional tests

are made with 4 available two-channel test stands.

The test is done after every step of assembly and includes: pedestal and noise measurements calibration charge inject silicon detector dark current


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HDI/Wedge Testing: Burn-

in Test

HDI/Wedge Testing: Burn-

in Test HDI, ladders and wedges burn-in is done

with 2 16-channel test stands. The devices are tested at low temperature (about 5oC) for up to 72 hours.

SVX gains, noise, pedestals, sparse mode and silicon detector dark current are

tested.


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Wedge Testing: Laser Test

Wedge Testing: Laser Test

HCB-126 Active Region 3/14/00

-20

0

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0 128 256 384 512 640 768

Channel

Am

pli

tud

e -

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5.0

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25.0

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35.0

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Stdev

2 infrared laser stands are used for final certification of the devices. Over 10 units per day

can be tested. Number of dead channels, detector depletion voltage, noise level are determined


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Test stands (continue)Test stands (continue)

10% system test stand is used for final system evaluation (cosmic ray test, barrel/disk tests)


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Diagnostics and Repair

Diagnostics and Repair

Diagnosis of problems with HDIs and detector assemblies is a major concern. Several microscopes, probe stations and logic analyzers are in use

Repairs of found faults: SVX chip replacement, wire bonding and pulling, flex circuits traces defects are made by a team of skilled technicians.


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Assembly of Full Wedge

Assembly of Full Wedge

Full wedge is made of two half wedges glued together. It is a double sided device with a stereo angle of 15 degrees.

Assembly made on a bi-facial machine with two microscopes.Typical accuracy 5 -10 . Up two wedges per day can be made.

Upper microscope

Lower Microscope

Assembled wedge


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Scheme of By-Facial Machine

Scheme of By-Facial Machine

Upper camera

Lower Camera

Accurate alignment of two cameras in angle and X-Y positions required


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Full wedge assembly

Full wedge assembly

Assembled full wedge on the flipping fixture ready for control measurements


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Ring AssemblyRing Assembly

This a prototype ring with mockup wedges and carbon fiber shroud

ring to hold HDIs tails and connectors with cables


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Ring Assembly (continued)

Ring Assembly (continued)

H-DISK beryllium cooling channels are assembled and leak tested


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H-disk AssemblyH-disk Assembly

Wedges are assembled on the cooling channel with a Coordinate-Measuring Machine (CMM) Zeiss-500. Thermal grease is applied for good contact between the cooling channel and wedges. Assembly accuracy is better that 10 .


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Production YieldsProduction Yields

Step Made Accepted Percent Silicon detectors1200 480 40 HDI assembly 210 157 75

Module assembly 150 120 80 Disk assembly 90 ?

Initial silicon/final device 100/30

Initial flex/final device 100/50


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H-disk Assembly Status:

H-disk Assembly Status:

125 grade A (<3% dead channels) and 17 grade B (3-10% dead channels ) devices (half wedges) are produced ( 75%) Note: average D0 SMT module production is about 50%.

Yield of grade A devices made during production period started in October 99 is about 90%

Full wedges are under assembly and 11 devices are ready

Disk assembly has started, first one is due in April

Goal: finish H-disk construction by fall 2000


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H Disk Status(in detail)H Disk Status(in detail)

Sensors OK except order of 15% (60 sensors) should be delivered before June

HDIs (192 needed) 218 laminated 162 stuffed (80%

yield) Half-Wedges (192 needed)

156 built including 11 mechanical grade ones 145 electrical grade wedges assembled: 84 were tested: 67(80%) graded as grade A (less then 3% of bad channels) 17(20%) grated as grade B

Full-Wedge(96 needed) 8 electrical and 4 mechanical built

Beryllium cooling rings (4 needed) all four fully manufactured, tested and ready for assembly

Assembly of the first mechanical H-disk ring has started with mechanical wedges


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HDI (High Density Interconnect) - Hybrid circuit Fabrication and Testing

HDI (High Density Interconnect) - Hybrid circuit Fabrication and Testing

Order bare flex circuit boards and probe them for shorts and discontinues (CSUF) - DONE

Lamination on beryllium substrates (FNAL) - 75% DONE

Surface Mount, die attach, wire bond chips to HDI substrate (Promex,Silitronics) - 65% DONE

Functional Tests Run (CSUF, KU, KSU, FNAL)- 65% DONE

Burn-in Tests(FNAL) - 65% DONE Repair and Rework - CAN BE FINISHED

AS THE DETECTOR COMPLETED!


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Production MilestonesProduction Milestones

10/15/99 - H- half wedge fab 20% complete - DONE

2/23/00 - H- half wedge fab 80% complete - DONE

4/10/00 -first H-disk assembled

10/2/00- H-disks ready to be installed

These are only production milestones,

we have to have working detector.


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Characteristics of Assembled

Devices

Characteristics of Assembled

DevicesDistribution of number of dead channels for H-disk half wedges after bond pulling and tests.

0

2

4

6

8

10

12

14

16

18

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3 6 9 12 15 18 21 24 27 30 33 40 50

Number of dead channels

Qu

ant.

Of

HW

edg

es

3 HWs52 HWs

A-grade(Nd<3%)B-grade(3<Nd<6%)


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H-disk Production Yields

H-disk Production Yields

HW production and testing summary:(except results of production and testing before October 99.)

Status HEA HEB HCA HCB Total Total were

assembled

Grade A 15 7 18 19 59Grade B 2 1 3 1 7 C@M 1 0 2 0 3

1/4Ws 0 0 0 0 0HWs fun-test 0 0 0 0 0HW burn-in 9 16 14 11 50HWs repair 0 0 0 0 0HWs laser 1 4 3 3 11

All: A@notest 25 27 35 33 120Yield:(A + 0.95*notest)/all 0.88 0.93 0.85 0.95 0.90 130


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Conclusions and Perspectives

Conclusions and Perspectives

The H-disk construction is on track.

The assembly, installation and commissioning at D0 will be completed in the end of the year.

The developed techniques can be used for the proposed D0 upgrade (Layer 1,2) to assemble two singe sided radiation hard silicon sensors

Acquired experience will be useful for future work on large area silicon trackers for B-TEV and CMS.


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Perspectives:Perspectives:

use new type of adhesive (re-workable, thermo- ( if needed electrical-) conductive 3M film for large area detector assembly

use bi-facial machine to make double sided silicon assembly with single sided detectors with high precision

use high depletion voltage devices with over depletion up to 150 volts at low temperature below 0o C)

mikhail kubantsev - kansas state university 1 assembly of a large area microstrip silicon tracker...

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