Mikhail Kubantsev - Kansas State University 1 Assembly of a Large Area Microstrip Silicon Tracker Some Experience of Construction of D0 SMT H- disk Silicon Detectors March

Mikhail Kubantsev - Kansas State University 2 Outline 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

Mikhail Kubantsev - Kansas State University 3 Experiment D0 Silicon Microstrip Tracker  Scintillating fiber tracker

Mikhail Kubantsev - Kansas State University 4 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 BARREL S

Mikhail Kubantsev - Kansas State University 5 Silicon 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

Mikhail Kubantsev - Kansas State University 6 SMT 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

Mikhail Kubantsev - Kansas State University 7 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 0 o C so they have to be in dry atmosphere (nitrogen gas)  Mixture of water and ethylene glycol is used as a coolant at temperature of -10 o C

Mikhail Kubantsev - Kansas State University 8 Track Measurements by H-disks  H-disk subsystem is a tracking device and not a vertex detector measuring tracks in rapidity interval Particle momentum is measured in r-  plane (magnetic field is normal to the disk).  Detector position accuracy of  is expected  The track momentum is measured by combination of barrel ladders (vertex position), F-disks and H-disks.

Mikhail Kubantsev - Kansas State University 9 H-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:

Mikhail Kubantsev - Kansas State University 10 Structure of the H-disk H-disk shroud Beryllium cooling channel Scintillating fiber tracker barrel 24 wedges installed on the cooling channel

Mikhail Kubantsev - Kansas State University 11 Half Wedge - Basic Module of the H-disk Outer silicon sensor (under Be substrate and HDI) Inner silicon sensor Be substrate HDI 65 cm 2 area of silicon

Mikhail Kubantsev - Kansas State University 12 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

Mikhail Kubantsev - Kansas State University 13 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

Mikhail Kubantsev - Kansas State University 14 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

Mikhail Kubantsev - Kansas State University 15 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

Mikhail Kubantsev - Kansas State University 16 H-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

Mikhail Kubantsev - Kansas State University 17 HDI-Beryllium Lamination  Set up 2 sandwiches of parts on the special fixture: the bare HDI, epoxy glue film, Be substrate, conductive epoxy glue

Mikhail Kubantsev - Kansas State University 18 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

Mikhail Kubantsev - Kansas State University 19 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 Resolutio n Product - a stuffed HDI: Present yield - 80%

Mikhail Kubantsev - Kansas State University 20 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

Mikhail Kubantsev - Kansas State University 21 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.

Mikhail Kubantsev - Kansas State University 22 Wire 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  Over 2000 bonds per half wedge are made in less than 30 minutes SVX chip wire bonding to the flex circuit

Mikhail Kubantsev - Kansas State University 23 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.

Mikhail Kubantsev - Kansas State University 24 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

Mikhail Kubantsev - Kansas State University 25 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

Mikhail Kubantsev - Kansas State University 26 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 5 o C) for up to 72 hours. SVX gains, noise, pedestals, sparse mode and silicon detector dark current are tested.

Mikhail Kubantsev - Kansas State University 27 Wedge Testing: Laser Test 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

Mikhail Kubantsev - Kansas State University 28 Test stands (continue)  10% system test stand is used for final system evaluation (cosmic ray test, barrel/disk tests)

Mikhail Kubantsev - Kansas State University 29 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.

Mikhail Kubantsev - Kansas State University 30 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 . Up two wedges per day can be made. Upper microscope Lower Microscope Assembled wedge

Mikhail Kubantsev - Kansas State University 31 Scheme of By-Facial Machine Upper camera Lower Camera Accurate alignment of two cameras in angle and X-Y positions required

Mikhail Kubantsev - Kansas State University 32 Full wedge assembly  Assembled full wedge on the flipping fixture ready for control measurements

Mikhail Kubantsev - Kansas State University 33 Ring Assembly This a prototype ring with mockup wedges and carbon fiber shroud ring to hold HDIs tails and connectors with cables

Mikhail Kubantsev - Kansas State University 34 Ring Assembly (continued)  H-DISK beryllium cooling channels are assembled and leak tested

Mikhail Kubantsev - Kansas State University 35 H-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 .

Mikhail Kubantsev - Kansas State University 36 Production Yields  Step Made Accepted PercentSilicon detectors HDI assembly Module assembly Disk assembly 90 ?  Initial silicon/final device 100/30  Initial flex/final device 100/50

Mikhail Kubantsev - Kansas State University 37 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

Mikhail Kubantsev - Kansas State University 38 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

Mikhail Kubantsev - Kansas State University 39 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!

Mikhail Kubantsev - Kansas State University 40 Production 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.

Mikhail Kubantsev - Kansas State University 41 Characteristics of Assembled Devices A-grade(Nd<3%) B-grade(3<Nd<6%)

Mikhail Kubantsev - Kansas State University 42 H-disk Production Yields

Mikhail Kubantsev - Kansas State University 43 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.

Mikhail Kubantsev - Kansas State University 44 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 0 o C)