columbia university in the city of new york roc3' / preproduction roc design status e.j. mannel...

Columbia UniversityIN THE CITY OF NEW YORK

ROC3' / preproduction ROC Design Status

E.J. MannelStriPixel ReviewOctober 1, 2008

09/30/08

Eric J. [email protected]

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Strip Ladder Conceptual Design(Details to follow)

ROC ROC ROC ROC ROC BUS Ladder DataTransfer Board FEM

DCM

Top View of ladder

Bottom View of Ladder

RCC RCC RCC RCC RCC

Carbon Fiber Stave and Cooling(Light Blue) Optical Fiber

BUS

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Strip Read Out Card (ROC)

Strip ROC consists of: StriPixel Silicon sensor

768 (6*128) X channels 768 (6*128) U channels split equally in to 3cm x 3cm region

12 SVX4 readout chips Passive component for SVX4 chips Interconnect with RCC module

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interconnect

ROC Module-Concept

Stripixel Sensor

svx4

svx4

svx4

svx4

svx4

svx4

svx4

svx4

svx4

svx4

svx4

svx4

connector connector

Routing of SVX4Control/Data Signals

Location of Passive components

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Readout Control Chip (RCC) Module Connects to the ROC- 1 RCC per ROC Contains Rad-Hard Readout Control Chip (RCC)-

Custom ASIC or FPGA Controls read out of the 12 SVX4 chips on ROC Multiplexes data onto readout bus Translates/passes LVDS signals to the SVX4s

Located on back side of strip ladder. Has passive components for power filtering. Connects to Ladder Data Transfer Board (LDTB)

via Ladder Bus Flex circuit construction

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RCC Module-Concept

ROC Connector

ROC Connector

BusConnector

RCC

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Ladder Bus

Connects multiple (5/6) RCC modules to Ladder Data transfer Board (LDTB)

Flex Circuit construction Mounted on bottom of ladder, extending

into Big-Wheel Region. No active components Possibly passive components for LVDS

termination (Details to be worked out)

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Ladder Data Transfer Board(LDTB)

Located in Big-Wheel Region of VTX Rad-Tolerant FPGA

Translates the LVDS <-> Serial (SERDES) Strips channel numbers from the SVX4 data

Receives/transmits data from/to the FEM via optical fiber BCO-Mode Bits-Slow control data

Power regulation for ROC/RCC modules Rigid-Flex board design

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Strip Front End Module (FEM)

Receives/Sends optical data from/to LDTB Data reduction and reformatting:

Real time pedestal subtraction Zero Suppression Adds PHENIX standard data headers and tails

Optical interface to DCM2 Optical interface with GTM

Sends BCO/Mode bits to LDTB Interface with slow control system

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Strip Ladder Conceptual Design

ROC ROC ROC ROC ROC BUS Ladder DataTransfer Board FEM

DCM

Top View of ladder

Bottom View of Ladder

RCC RCC RCC RCC RCC

Carbon Fiber Stave and Cooling(Light Blue) Optical Fiber

BUS

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ROC2

First attempt to place ReadOut Card (ROC) in top of stripixel sensor Observed pedestal shifts attributed to capacitive

coupling in the sensor and poor ground plane design

Internal review of the ROC2 in July 2007 Recommendations led to ROC3 design Rachid's presentation has shown results from the

ROC3 module

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ROC3

Review Recommendations: Move readout chips to side of sensor Improve ground planes. Optimization of board stackup

Not intended as a ladder ROC First modules available early 2008 Used successfully in the FNAL Beam Test

(FNAL-T984) effort in the summer of 2008 Lessons learned were used for ROC3'

design

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ROC3'

Minimal redesign of ROC3 to improve ease and yield of the fabrication and assembly of the ROC module

Verify reproducibility of ROC3 performance

Study the impact of changes in the overall board thickness and thickness of copper layers

Study the impact of moving/reducing passive components on the ROC

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ROC3' Design

Maintain the same stack up as ROC31)Analog ground/ Components2)Analog Power/ Digital Ground3)Digital Signal4)Digital Power/Digital Signal5)Digital Ground

Wire bond SVX4 I/O pads directly to inner layer traces Requires a milled opening or cavity through first

two layers of board All components on top of the ROC

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ROC3' Design Changes

Increased size of wire bond pads where possible

Relocated passive components to improve wire bonding if possible

Increase size of opening to access inner layer for wire bonding of SVX4 I/O connections

Reduce overall board thickness Produce board with both ½ oz and ¼ oz

copper layers

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ROC3' Summary

ROC3' is a success: Analog performance matched or exceeded

ROC3 performance (Rachid's Talk) Easier to fabricate (Hughes Circuits) Easier to assemble (Hughes Circuits/BNL-

Instrumentation/SiDet) Thinner boards (overall/Cu thickness) perform

well Will reduce the overall radiation thickness of

the strip ladder

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ROC3' Summary Still some fabrication and assembly issues

to be addressed: Attachment process of the bias plane to the ROC

still needs improvement. Opening to inner layers of ROC for wire bonding

of SVX4 still difficult. Clearances still an issue:

bond pad contamination (solder, flux, etc.) ¼ oz Cu version had yield problems.

ROC3' lessons lead to preproduction ROC design improvements

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preproduction ROC (ppROC) Goals

Maintains or surpasses the ROC3/ROC3' performance.

Meets or exceeds the baseline design specifications: overall dimensions. radiation length.

Increasing the yield and reducing the cost. Not adversely effecting the VTX

installation schedule.

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ppROC Design

Discussions with over the last month: VTX group to discuss global strip ladder

design Catalyst Microtech, Austin TX.

Wire Bonding Company Hughes Circuits, San Marcos CA

Board Manufacturer/Assembler HYTEC, Los Alamos NM

VTX/FVTX Engineering firm

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Discussion Summary

Suggestions: Increase die pad size for SVX4 Solder, not glue, SVX4 to ROC Increase wire bond pad size Passive components on bottom, not top Increase keep out space around bond pads Eliminate wire bonding to inner layer of ROC Aluminum wire bonding is better then gold Larger clearances/traces for improved yield

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Discussion Summary Cont....

Place ROC-RCC connection on bottom of ROC Design staves with no opening for bottom

mounted components Use stave design similar to ATLAS design Glue bus to bottom of stave Use some type of alignment pins to insure

alignment of ROC/RCC/Bus during assembly process.

Recommendations playing a leading role in design of the ppROC

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ROC3' Passive Component Issue

High density of components between SVX4s:

Requires stacking of some components- 0201 on 0402

Interference with wire-bonding

Tight tolerance: 3 mil clearance

Chance that solder mask will not flow properly

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ppROC Passive Component Solution

Move components to back side: More area available

for components No need to stack

components No issues with pad

contamination Allows repositioning

and enlargening of bond pads

Yellow top layerMagenta inner layersGreen bottom Layer

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ROC3' Bias Plane Attachment Issue

Attached separately after surface mount components are attached by hand.

Required due to 0201 components on the top

Attachment technique results in uneven surface for svx4s and sensor

Labor intensive

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ppROC Bias Plane Attachment Solution

Bias plane can be laminated on. Requires surface mount components on back side Allows use of solder balls in vias and re-flow to

make electrical connection between layers. Allows placement of connections for bias voltage

under the sensor Connection points should be level and not

interfere with sensor or SVX4s

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ROC3' SVX4 I/O Pad Opening Issue

12 slots milled through top 2 layers to expose inner layer bond pads

Milled after board lamination.

Risk of damaging inner layer (yield)

Increases difficulty of wire-bonding.

Wire bond pads are narrow, 4 mils

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ppROC SVX4 I/O Pad OpeningSolution

Move bond pads to top layer

Stagger pads to allow wider pads for bonding (not shown)

Reduces problems with wire bonding

Bond Pad regionTraces on top

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ROC3' Overall Flatness Issue

Small amount of warpage in board Result of:

Thin boards Asymmetric stack-up

Very little can be done given the design-Inherent in the board design and fabrication process.

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ROC3' ¼ Oz Copper Issues

Loss of electrical connectivity on board Result of fabrication steps

¼ oz Cu = .35 mil thick Different steps can remove some of the copper Cobra step most damaging Results in loss of electrical continuity on traces

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ppROC ¼ Oz Copper Solution

½ oz Cu on trace planes. Wider traces where possible No need for Cobra step on trace planes.

part of the fabrication process Make ground and power planes ¼ oz Cu.

Will reduce overall board radiation thickness

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ppROC-RCC Connection

Propose using interposer solution from Paricon Well established technology High reliability: Connection pads on RCC and ppROC are mated

with PariPoser material in between. Applied force maintains connection- requires

carbon fiber stiffener on ppROC and RCC Can be used for signals, power and bias

connections

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ppROC-RCC Connection

Silicone insulator with vertical conduction paths

Placed between pads, compression makes the connection between surfaces

Alignment only of circuit boards required

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ppROC-RCC Interconnection

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Mechanical

Board Dimensions: Wide board design is baseline (SVX4s on the side

of the sensor). Maintain 80mm board width base line. Maintain 65mm board length base line

Baseline dimensions can be met: ppROC-RCC connection grid on bottom of ROC No flex cable to wrap around stave Component placement is still tight

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Mechanical Dimensions

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ppROC Work in Progress

New Schematic almost complete Changes for final ppROC-RCC connection required Move power filtering caps to the RCC

ppROC layout has started, but still work to be done. New ppROC-RCC connector Changes to SVX4 die pad size Change location and size of bond pads Change bias plane connections

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ppROC Schedule

Layout complete in early 4Q CY-2008 First ppROCs fabricated late 4Q CY-2008 First strip modules assembled early 1Q

CY-2009 First strip modules ready for system chain

test late 1Q CY-2009

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Conclusions

ROC3' performed as well as ROC3 Lessons learned from ROC3' will improve

ppROC design: Ease of fabrication and assembly Result in improved yield and lower cost

ppROC design will maintain baseline ladder design constaints and meet performance requirements

Time line is consistent with chain test in 1Q CY 2009

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Backup

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Concerns/Issues

Test of removing “extra” filter caps showed widening of pedestals for some SVX4s

columbia university in the city of new york roc3' / preproduction roc design status e.j. mannel...

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