1 / 30

Outline

Prototype flex hybrid and module designs for the ATLAS Inner Detector Upgrade Ashley Greenall The University of Liverpool On behalf of the ATLAS Tracker Silicon Strip Upgrade Stave Programme. Outline. Introduction to the Stave (2009) concept Geometry and components

jered
Download Presentation

Outline

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Prototype flex hybrid and module designs for the ATLAS Inner Detector UpgradeAshley Greenall The University of LiverpoolOn behalf of the ATLAS Tracker Silicon Strip Upgrade Stave Programme Topical Workshop on Electronics for Particle Physics Paris, September 21-25, 2009

  2. Outline • Introduction to the Stave (2009) concept • Geometry and components • Stave flex hybrid, first steps • Build considerations - preparing for mass production • Prototype flex, a test vehicle for the 0.25µm ABCN-25 ASIC • Electrical performance (using untested ABCN-25) • Short strip module demonstrator using ATLAS07 large area sensor (10cm x 10cm) • Bridged Hybrid • Hybrid directly glued onto sensor • Summary • First stave module, a substrate-less and connector-less module • Module concept and flex build • Current substrate-less hybrids • Substrate-less stave hybrids and industrialisation • Stave Readout architecture • A first look at module integration onto a stave • Conclusions Topical Workshop on Electronics for Particle Physics Paris, September 21-25, 2009

  3. Stave 2009 – Geometry and components • P-type 4 segment crystals (10cm x 10cm) • ABCN-25 readout ASIC • 40 per module • 960 per stave (>120k channels) • Kapton hybrid • Auxiliary BCC asic (digital I/O) • Serial Power protection • Embedded bus cable • End of stave card • Stave mechanical core Sensor 12 modules/side of stave Single flex Module with 2 x flex 120mm ~ 1.2m (1200mm) Carbon fiber facing Bus cable Carbon honeycomb Readout IC’s Hybrids Coolant tube structure Topical Workshop on Electronics for Particle Physics Paris, September 21-25, 2009 3

  4. Stave flex hybrid – Build considerations • Hybrid layout is driven by minimising material • Keep the area small! Engage ASIC and sensor designers to achieve this. • Eventually we will want to source in excess of 10000 pieces (for Barrel short-strip layers) • Yield and reliability has to be taken into account from the outset • Don’t push the limits on design rules (pertinent to feature size) • Repeatability becomes problematic for non-standard capability – limits vendor choice • Manufacturability, feedback from UK (flex) manufacturers: • Keep to standard 100µm track and gap routing to maintain yield • Identified via lands (for plated-through holes) as critical, need to be >300µm • Ref: CMS had many problems with micro-vias (had to increase to 320µm to recover yield/stability) • Settled on 375µm via lands with 150µm laser drilled holes • Kapton carrier (dielectric) should be no thinner than 50µm – handling issues during manufacture • Will be a staged design • First stage – very cautious, new ASICs and sensors to be evaluated THIS IS WHERE WE ARE • Flex build is electrically ‘robust’ – maximal power planes and supply decoupling • Second more aggressive stage – comes much later, • Reduction in hybrid mass (removal of non-critical passives, power plane reduction etc.) Topical Workshop on Electronics for Particle Physics Paris, September 21-25, 2009 4

  5. Prototype flex topology Common Bus serving 20 x ABCN-25 Column 1 Column 0 • Consists of 2 columns of ABCN-25s with a services connector • Readout Architecture is made up of • Single TTC Bus (BCOClk, Com, L1, DataClk) • Power Control Bus for serial powering circuitry • Auxiliary Analogue Supply routed to front-end of ABCN-25s • Alternatively make use onboard regulator for the front-end • Common Digital Supply provided for ABCN-25s • Legacy data paths at top and bottom of each column (maintains compatibility with existing DAQ) • Bi-directional data paths within columns can be exercised • Data & Token I/O for 2 leading ABCN-25s for use with an upgraded DAQ (if desired) M M TTC & Power Control Bus S S Primary Data O/P S S S S S S Redundant Data O/P S S S S MCC I/O (Data + Token) S S S S M: Master (Legacy mode) Mm: Master (Legacy mode + MCC I/O) S: Slave Mm Mm Connector Topical Workshop on Electronics for Particle Physics Paris, September 21-25, 2009 5

  6. ASIC – Sensor Detail Dialogue with designers • Early dialogue with ASIC and sensor designers lead to modifications to increase manufacturability and reduce mass... • Wire bond pad locations and ASIC size/placement fixed to allow for direct ASIC-to-sensor wire bonding • Pitch adaptors are no longer required • Less mass and wire bonds • ASIC bond pads re-located: • Inter-chip communication now provided by wire bonds and not traces on the flex. • Front-end decoupling capacitor positioned for shortest bond length. Front-end Decoupling Capacitor Sensor bond pads <16° bond angle 4.1mm Topical Workshop on Electronics for Particle Physics Paris, September 21-25, 2009 6

  7. Flex build details Vias • 4 layer build designed to qualify components i.e. ASICs and sensors and to prove signalling quality as fast as possible • Layer 1 & 2: Signal • Layer3: Analogue and Digital Power • Layer4: Common Ground • Flex manufactured by Stevenage Circuits Ltd UK • 100µm track and gap • 375µm via lands with 150µm laser drilled holes • 50µm Kapton (polyimide) dielectrics Component Layer Digital Bus Analogue Power Digital Power Common Ground Solder Resist (25µm) 5µm Cu foil carrier + Ni/Au plating (5µm) Bond ply (50µm) Cu (18µm) Kapton (50µm) Predicted build thickness is ~260µm, actual is ~280µm (uncertainty arises due to plating of outer layers) Topical Workshop on Electronics for Particle Physics Paris, September 21-25, 2009 7

  8. Hybrid realisation Neighbouring ABCN-25s wire bonded Inter-chip bonding 24mm 7.5mm 2.1mm 7.5mm 100mm Distributed decoupling capacitors adjacent to the ASICs for power supply decoupling - capacitance increases whilst inductance reduces (improves high frequency decoupling) Sensor HV filter with guard ring Flex Weight ≤2g (unpopulated) Fully populated hybrid Hybrid Stuffed with Passives and 6 x ABCN-25s 8 Topical Workshop on Electronics for Particle Physics Paris, September 21-25, 2009

  9. Electrical Performance – Signal Propagation • Transmission of fast LVDS signals (expected to be 160MHz for next generation ASICs), need to account • Use of thin dielectrics for flex build, results in a high capacitance (~25pF on a 100m trace) further loading the bus • Bus loading (up to 20 ASICs max) • Trace impedance set by width, thickness of dielectric and dielectric constant. • Hybrid topology makes use of embedded edge-strip geometry for LVDS transmission. • For proposed build using 100µm track and gap with 50µm dielectrics, ZDIFF ~ 71Ω. • But this does not take into account asic receiver loading (see plot below). • 20 ASICs on bus reduces impedance to <50Ω. Eye diagrams for 20 ASIC Loading 80Mbs PRBS 43Ω end termination (2ns/div, 50mV/div) Unloaded Bus Loaded Bus 160Mbs PRBS 43Ω end termination (2ns/div, 50mV/div) Topical Workshop on Electronics for Particle Physics Paris, September 21-25, 2009 9

  10. Electrical Performance – Hybrid results • Hybrid tested at both 40MHz and 80MHz data rates (maximum that ABCN-25 operates at) • All 4 data paths from hybrid work - confirming ABCN-25 bi-directional I/O functions correctly 40MHz data readout 80MHz data readout Channel threshold spread ENC vs Channel ENC vs Channel After trimming Noise Occupancy Channel threshold spread Occupancy vs Channel ENC vs Channel • Gain: 105mV/fC • Input Noise: ≤400e ENC • Threshold variation: 5.5mV before trimming, 1mV after trimming ASICs and hybrids working extremely well with high yield Topical Workshop on Electronics for Particle Physics Paris, September 21-25, 2009 10

  11. Short-strip module demonstrator with 10x10cm sensor • Overview • Al plate with machined bridge legs and cooling pipe (10°C glycol + water) • Sensor glued directly to fixture • 2 layers of 75µm thick kapton between Al plate and sensor • HV connection through tab to backplane • Al plate referenced to ground of hybrid • First hybrid bridged with 1mm thick Al • 2mm air gap between hybrid and sensor • Second hybrid directly glued to sensor • Objective • Test the functionality of the ABCN-25 in a 20 ASIC hybrid bonded to a full size ATLAS07 sensor • Using untested ASICs • Check the noise performance and occupancy • Stability at low threshold of 0.5fC Topical Workshop on Electronics for Particle Physics Paris, September 21-25, 2009 11 ATLAS Tracker Upgrade Week, 23rd-27th Feb 09

  12. First tests – Bridged hybrid • Bridge grounded to plate • Thermal grease applied to cooling points • Hybrid operating at 40°C i.e. 30° above coolant temperature (coolant at 10°C) • Peak currents >4A during readout • Token passing non-functioning between chips 5 and 6 (damaged bond pad) • All chips work BUT only able to readout 15 chips at a time • Noise Slope • Able to join 2.5cm segments of sensor to single ABCN-25 e.g. 2.5cm, 5cm and 7cm strip lengths • Also have bare hybrid plus 1cm silicon strip measurement • Sensor design provides 1pF/cm load 2.5cm 5cm 7.5cm Topical Workshop on Electronics for Particle Physics Paris, September 21-25, 2009 12 ATLAS Tracker Upgrade Week, 23rd-27th Feb 09

  13. Preliminary Noise slope Noise prediction from ASIC designers with no detector leakage Measured noise is slightly higher than that expected from simulation – especially above 2.5pF load Topical Workshop on Electronics for Particle Physics Paris, September 21-25, 2009 13 ATLAS Tracker Upgrade Week, 23rd-27th Feb 09

  14. Bridged Hybrid Electrical Performance Noise Occupancy Occupancy vs Channel ENC vs Channel • Module tested with front-end regulator enabled • Single Digital power feed to all ASICs • Input Noise is as expected at ~600e- • Open circuit channels are due to wire-bonding problems • Al plate hybrid is mounted on is not rigid enough – makes it difficult to bond • Noise Occupancy at 1fC is <10-6 • Shows a very regular uniform profile across all channels • Clearly shows the 5 ASICs we are unable to readout Topical Workshop on Electronics for Particle Physics Paris, September 21-25, 2009 14 ATLAS Tracker Upgrade Week, 23rd-27th Feb 09

  15. Directly Glued Hybrid on to Sensor • Hybrid was not designed to be glued directly to sensor • Vias go right through the flex circuit – results in a perforated ground plane • No shielding of the digital bus is provided • Copper shield added between hybrid and sensor • Insulated from hybrid and sensor • Can be referenced to hybrid ground if desired • Hybrid operates at 24°C during readout (compare with the bridged hybrid of 40°C) Hybrid Glue was only applied on passivated regions of sensor, maintaining a clearance of 5mm from the guard-rings. Kapton (75 mm) Copper (75 mm) Kapton (150 mm) Glue(~20 mm) Passivation p-spray/stop p- bulk Topical Workshop on Electronics for Particle Physics Paris, September 21-25, 2009 15 ATLAS Tracker Upgrade Week, 23rd-27th Feb 09

  16. Glued Hybrid Electrical Performance Shield Connected Shield Open Circuit ENC vs Channel ENC vs Channel • With the screen connected • To either module ground or HVret • Channels towards the edges of the ASICs have elevated noise • Input noise is ~650e- • With the screen floating • Noise profile is flat • Input noise is ≤600e- • Performance is comparable to Bridged Hybrid Occupancy vs Channel Topical Workshop on Electronics for Particle Physics Paris, September 21-25, 2009 16 ATLAS Tracker Upgrade Week, 23rd-27th Feb 09

  17. Glued Hybrid Electrical Performance – Low Threshold Stability Scurve distortion is due to wire-bonding (see next slide) Scurves at 0.5fC threshold show no instability with 2.5cm sensor strips bonded Topical Workshop on Electronics for Particle Physics Paris, September 21-25, 2009 17 ATLAS Tracker Upgrade Week, 23rd-27th Feb 09

  18. Wire-Bonding Problems • Identified that glued hybrid is 400µm off centre w.r.t. sensor • Results in increased bond-angle from ASIC to chip • Bonds at chip-edges are at 12-21° angle • Anything >16° is at risk of shorting to neighbouring bond pads on ABCN-25 • This is what we see on the noise plots • Problem with bonding of front-end ground pads • Wire bonds are orthogonal to pad • Pad is too narrow for the bond foot • Adhesion of bonds is not so good • Revised layout of flex will correct for this Topical Workshop on Electronics for Particle Physics Paris, September 21-25, 2009 18 ATLAS Tracker Upgrade Week, 23rd-27th Feb 09

  19. Prototype flex/module Summary • First batch of flexes arrived towards the end of last year – 36 total • Yield of 89% was achieved • Should increase to ≥98% during production run (achieved by process tuning) • Yield enhancement is part of the design stage – high yield translates into a reliable object • Hybrid performs as expected – untested ASICs • Hybrids have been successfully used at 4 different sites • Wire-bonded at 2 sites with no problems • For the module, bridged and glued hybrids have similar electrical performance • Both stable at 0.5fC threshold • Noise is higher than predicted from simulation • No show stoppers identified for Stave hybrid Topical Workshop on Electronics for Particle Physics Paris, September 21-25, 2009 19 ATLAS Tracker Upgrade Week, 23rd-27th Feb 09

  20. Stave Module Concept • Flex circuit is designed at the outset for direct gluing to the sensor • Core of the circuit (trace routing, component placement remains as prototype) – it works • But will have to revise the flex build to take into account additional shield layer • Sensor provides mechanical support and thermal management • Prior to gluing the flex circuit to the sensor the flex is not rigid • Need to stuff with passives/ASICs and then test before gluing on to the sensor Furthermore • Have to take into account integration of the module on to a stave • Stave design calls for a connector-less system • All connectivity is made by wire-bonds to/from a bus cable • Bus cable is a single-layer design – results in connections at opposing ends of flex • Would like to maintain maximum flexibility for stave module – especially true for powering • Default powering is serial • But power/protection board has provision for auxiliary plug-in boards (for DC-DC, etc/) • Also start looking at industrialisation of flexes • Component stuffing and testing Topical Workshop on Electronics for Particle Physics Paris, September 21-25, 2009 20 ATLAS Tracker Upgrade Week, 23rd-27th Feb 09

  21. Stave Module Layout 6.2mm Digital I/O - BCC TTC & Data Bus 5mm ‘M’ Shunt Regulation Control Circuit Sensor • Flex is a 4+1 layer build (4 electrical + shield layer) • Layer 1 Signal • Layer 2-3 Signal/Power • Layer 4 Non-split Ground • Layer 5 Shield (single-point contact with option to connect to module ‘ground’ or leave open) • Inner layer Cu thickness is 18µm • Top layer is 5µm Cu with Ni/Au plating • Shield is 5µm Cu • Kapton dielectric thickness is 50µm • Total build thickness is ~300µm 24mm 97.6mm ABCN-25flex ABCN-25flex Sensor HV Filter Circuit + Power In/Out to flex 5mm 6.2mm Power/Protection Board Serial Power, Control & Sensor Bias Topical Workshop on Electronics for Particle Physics Paris, September 21-25, 2009 21 ATLAS Tracker Upgrade Week, 23rd-27th Feb 09

  22. Stave 2009 – Readout Architecture Module 1 Module 2 Module 12 Data BCC BCC BCC BCC BCC BCC BCC BCC TTC Digital I/O Serial powering PwrIn PWR Sensor bias PWR PWR PWR PWR PWR PwrOut • TTC (L1, Command and 40MHz clock) is broadcast as multi-drop LVDS to all modules • 24 drops in total with ac-coupled receivers • Non-balanced data transmission • 2 data output links per module, 1 per flex • Point-to-point LVDS • Up to 160Mbs data rate • AC-coupled, non-balanced data transmission • Default powering scheme is serial • Flexes sat at differing voltage potentials (2.5V per flex, 60V total across a stave) • Parallel (DC-DC) powering is also provided for • Independent parallel sensor biasing (12 x HVbias + return) • Single NTC thermistor per flex for temperature monitoring BufferControlChip provides digital I/O Topical Workshop on Electronics for Particle Physics Paris, September 21-25, 2009 22

  23. How to make a substrate-less hybrid • Initiated a program to investigate working with substrate-less hybrids • Try to learn as much as possible from the pixel community • Kindly sent jigs to show steps involved in their module construction (see below) • Dialogue set up with both flex and circuit population companies. Sacrificial ends • Flex circuit composed of 2 components • Main active circuit (non-glued) • Sacrificial ends which are glued to FR4 • Circuit sits flat on a rigid FR4 base • Drilled for vacuuming down Step 1 Main circuit I/O bond pads Sacrificial ends (retained) Step 3 Step 2 Final step, circuit + sensor removed Topical Workshop on Electronics for Particle Physics Paris, September 21-25, 2009 23 ATLAS Tracker Upgrade Week, 23rd-27th Feb 09

  24. Stave substrate-less hybrids and industrialisation DAQ Connector(s) Active part of flex – not glued to FR4 Bond pads Score line is used as guide for cutting out of flexes Sacrificial ends of flex, cut off during flex removal (beyond score line) Power • Flexi-rigid construction with flexes selectively glued to a FR4 Panel. • 8 flexes per panel. • Panel is 300mm x 200mm. • Matches up to auto-placement machine (passive stuffing geared for industry) • Various hole detail shown are used for wire-bonding and module assembly jigs • Panel designed so that flexes can be electrically tested as 1 to 8 items (using legacy or future DAQ) Topical Workshop on Electronics for Particle Physics Paris, September 21-25, 2009 24 ATLAS Tracker Upgrade Week, 23rd-27th Feb 09

  25. Stave Integration – Bus Cable Detail • Modules (sensor + flex) glued onto stave – embedded bus cable sits between stave core and module • Bus cable used to distribute services to module(s) – digital I/O, power, sensor bias etc. – connections made by wire-bonds • Cable build is single layer Cu Kapton + Al shield on top layer (2 flavours of shield, segmented and continuous to be evaluated) Segmented Shield Detail (showing break between adjacent modules) Bus Detail (100µm track & gap) Continuous Shield Bond Pads Flexes are DC connected to their respective shield Flexes are AC connected to the shield TTC multi-drop Bus and Module Data Serial Power Return (7mm width) 120mm Power, Control & Sensor Bias 1200mm Plots courtesy of Carl Haber & Roy Wastie Topical Workshop on Electronics for Particle Physics Paris, September 21-25, 2009 25 ATLAS Tracker Upgrade Week, 23rd-27th Feb 09

  26. Conclusions • For the ATLAS Inner Detector and the large number of circuits required, it is important to plan at the outset for manufacturability and reliability. • Dialogue should be set up during the design phase between ASIC, hybrid and sensor designers. • This is also true for industrial partners • Hybrid operation has shown nothing untoward – performance is as expected! • Module demonstrator has also been shown to perform well • First time an ATLAS07 large area sensor has been bonded to full 20 x ABCN-25 readout • Noise is slightly higher than expected • BUT no show stoppers as yet identified • Have now migrated to ‘next generation’ hybrid designed for integration onto a stave. • Submission took place over the summer and flexes are due imminent. • If no problems identified expect flex passive/ASIC stuffing and testing in the near future. • Furthermore module integration onto a stave structure is well understood – now awaiting modules • Bus cables have been received and are ready for assembly on to a stave. Topical Workshop on Electronics for Particle Physics Paris, September 21-25, 2009 26 ATLAS Tracker Upgrade Week, 23rd-27th Feb 09

  27. Backup Topical Workshop on Electronics for Particle Physics Paris, September 21-25, 2009 27 ATLAS Tracker Upgrade Week, 23rd-27th Feb 09

  28. Sensor biasing and gluing • Concerns about gluing hybrid assembly directly to the sensor • Is there a risk of damaging the sensor – especially the sensitive guard ring structure • Limited maximum sensor bias to 200V • Reduces the risk of micro-discharge • Before assembly sensor current is 0.8µA • After gluing to Al fixture 0.8µA • After wire-bonding of front-end of bridged hybrid 3.1µA • After directly gluing of hybrid to sensor 2.9µA • After wire-bonding of front-end of glued hybrid 3.0µA • Some slight damage occurred during the wire-bonding of the bridged hybrid to the sensor • Otherwise no effect observed due to gluing of hybrid to sensor Topical Workshop on Electronics for Particle Physics Paris, September 21-25, 2009 28

  29. 24 GeV Proton Irradiation Results Before Irradiation, 20°C 2 Epolite glued miniature sensors were irradiated at CERN PS to 9.3×1014 neq cm-2. Before irradiation, W17-BZ3-P15 showed some breakdown above 950 V before gluing (blue circles). W31-BZ3-P9 goes to 1000V. After irradiation, W17-BZ3-P15 shows breakdown above 1000 V. W31-BZ3-P9 goes to 1100 V. The currents are consistent with the expected fluence. No measurable effects from the epoxy on the surface After Irradiation, -25 C Topical Workshop on Electronics for Particle Physics Paris, September 21-25, 2009 29

  30. 24 GeV Proton Irradiation Results (2) Irradiated to 1.5×1015 p cm-2 at CERN (9.3×1014 neq cm-2) No measurable effect of glue relative to similar irradiations Using fit of clustered charge, efficiency at 500 V near 100% at threshold of 1 fC for 1×1 cm2. Would expect 0.75 fC needed for 2.5 cm strips. Topical Workshop on Electronics for Particle Physics Paris, September 21-25, 2009 30

More Related