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Tony Weidberg 1
LightABLE Production Status
ID Week October 2014
ID Week October 2014
Tony Weidberg 2
LTx Project
• Aim: use commercial package for VCSEL array to improve reliability.
• LTx installed in crate 3 – BER from long physics
mode run ok– Problems with calibration
runs, required manual tweaking of MSR (slow!)
ID Week October 2014
LightABLE OSA (Reflex Photonics)
Production Status
• 500 LightABLEs delivered. • Assembly completed at Oxford.• Yields much lower than anticipated from
preproduction batch of 20– Mistakes in assembly procedure– Open circuits inside BGA after reflow process
• Hypothesis: due to delay between dryout and storage in dry N2.
– Total optical power high but OMA below threshold.
ID Week October 2014 Tony Weidberg 3
Tony Weidberg 4
Numbers• Available:
• 20 LTx which failed xBPM test being recovered by Mark.• Ordered 50 more LTx.
– Will be much more careful with all production steps expect higher yield.• Have ordered 50 LightABLE (8-12 week delivery)
– Z board and LightABLE PCBs assembled with all the other components.
ID Week October 2014
Cambridge QA yield 0.83installed crate 3 44at CERN 26cat A&B @ Cambridge 156 5at Oxford 146 121Rick recovered 3Total 355Required 354
Tony Weidberg 5
Backup
ID Week October 2014
Tony Weidberg 6
Changes Since Design Review
• Essential: – Make it easier for Infineon SMC connector to
connect to LTx in USA15– Improve thermal management
• Highly desirable: Allow option of decreasing optical power from LTx in case of saturation for DORIC4A.
• Mechanical reliability, consider use of under-fill for LightABLE BGA.
ID Week October 2014
Tony Weidberg 7
Mechanical Changes• Make mate/demate with Infineon
SMC easier.– Shortened length of MT guide
pins.– Added groove near end that was
cut to help with gluing. End sticking out is the uncut end.
– Use long guide pins in jig during reflow. Ensures that guide pins will be in the correct location and pointing the correct way.
ID Week October 2014
Tony Weidberg 8
Underfill
• Decided against use of underfill for BGA– Mismatch in CTE.– Very little insertion force required.– 100 mate/demate cycles with monitoring of power every
10 cycles no changes– Thermal cycling: no change in power.
ID Week October 2014
Tony Weidberg 9
Cooling• Thermal path from LightABLE to front panel
via Thermal Gap Filler (3 Wm/K)• OSA analysis DT from junction to ambient
=20°C ( next slide).
ID Week October 2014
Tony Weidberg 10
OSA Analysis
• Measure Peak wavelength lp• Scan Mark: Space Ratio (MSR)
and measure lp• Plot lp versus MSR• Fit slope and extrapolate to
50%.• Use calibration dlp/dT DT• Fit Results variable in quality
but reasonable consistency
ID Week October 2014
Tony Weidberg
AtLinks LightABLE- uProc
We can use a microprocessor to drive the LightABLE Engine’s I2C inputs, and the SPI lines currently used for the MDACs can be used to drive the µProc
But the MDACS we must still give the right output current for the interface circuit• This could be done using the µProc’s SPI lines• It could be carried out when the µProc is initialised• The MDAC_CLR command (one of the BOC_SPI signals) could be
used to force a uProc initialisation
This is what it would look like:
ID Week October 2014 11
Maurice Goodrick
Tony Weidberg
AtLinks LightABLE- uProc Connections
ID Week October 2014 12
Z PCB
Maurice Goodrick
Tony Weidberg 13
QA: Optical Power
ID Week October 2014
1 1.2 1.4 1.6 1.8 2 2.2 2.4 2.6 2.8 3 More0
5
10
15
20
25
30
35
40
45
LTx
Power (mW)
Freq
uenc
y
-2.4 -2 -1.6 -1.2 -0.8 -0.4 0 0.4 0.8 1.2 1.6 2 2.40
5
10
15
20
25
30
35
40
LTx
After - Before Burn-in (dB)
Freq
uenc
y
<Optical Power> @ 50% duty cycle,after burn-in
Change with burn-in (72 hours @70C)
Tony Weidberg 14
LTx in SR1
• LTx optical power.• No T correction• Initial decrease
~1%.– No burn-in
preformed for this array probably ok but should run longer
Steve McMahon
Opti
cal P
ower
(mV)
Time (days)ID Week October 2014
Tony Weidberg 15
Steve McMahonO
ptica
l Pow
er (m
V)
Time (days)ID Week October 2014
Tony Weidberg 16
Summary
• Improvements following design review have been implemented.
• Production well underway.• Populate one crate in USA-15 in May• Need to continue long-term optical power
monitoring in SR1 and USA-15.
ID Week October 2014
Backup Slides
ID Week October 2014 Tony Weidberg 17
Tony Weidberg 18
OSA Thermal Studies• New metalwork for front panel of BOC
– Takes heat through thermal pad metalwork outside crate• OSA measured for 12 channels from first LTx with micro on board.• OSA spectra taken at MSR settings of 0, 10, 20 and 24 (maximum
value which gave clean waveform).• Very crude peak finding
– Found lmax corresponding to maximum power
– Found l1 and l2 corresponding to peak power -3dB
– Best estimate lpeak= (l1 + l2)/2
– Used difference between lpeak and lmax as estimate of error.– Error on MSR set to 1% (guess)– Fit lpeak vs MSR next slides
ID Week October 2014
Tony Weidberg 19
Fit Results variable in quality but reasonable consistency
ID Week October 2014
Tony Weidberg 20
Check this point (see next slide)
ID Week October 2014
Tony Weidberg 21ID Week October 2014
Tony Weidberg 22
Check Channel 8 MSR=20• Spectra looks ok• Programme found reasonable results• 3 sigma effect doesn’t change conclusions
855 855.05 855.1 855.15 855.2 855.25 855.3 855.35 855.40.00E+00
5.00E-03
1.00E-02
1.50E-02
2.00E-02
2.50E-02
3.00E-02
3.50E-02
ch 8 MSR=20
ch 8 MSR=20
From programme:Max power @ 833.330 nmPeak @ 833.327 nmLooks ok?
ID Week October 2014
Tony Weidberg 23
Summary
• Fits to each channel for slope• Use Carlos’s analysis for temperature
sensitivity– dl/dT=0.0673 nm/K
• Extrapolate to 50% duty cycle• DT = 20 ± 4 C• Improved thermal performance compared
to previous study DT = 29 to 43 C. – Improved metalwork takes heat through
thermal pad to outside of crate.
channel slope
0 0.0273
1 0.0235
2 0.0242
3 0.0296
4 0.0241
5 0.0251
6 0.0260
7 0.0251
8 0.0445
9 0.0271
10 0.0280
11 0.0259
ID Week October 2014