GLAST LAT Project
March 24, 2003
GLAST Large Area Telescope:
Gamma-ray Large
Area Space
Telescope
Tracker Subsystem
WBS 4.1.4
6C: Ladder Fabrication
A. Brez
I.N.F.N. Pisa
Brez@pi.infn.it
6C
Tracker Peer Review, WBS 4.1.4
1
GLAST LAT Project
March 24, 2003
Ladder construction flow down
• LAT ladder construction follows the block diagram (see LAT-PS00635 and LAT-PS-00831 for details)
WS1: Receiving and
Inspection
Storage
WS2: SSD Edge
Bonding
WS5: Electrical
Tests
Storage
WS6: Wire-Bond
Encapsulation
WS3: Metrology
Storage
WS7: Encapsulation
Inspection
Storage
WS4: Wire Bonding
WS8: Electrical Tests
Storage
WS9: Storage of
Completed Ladders
Assembly in G&A Engineering (251 flight ladder produced)
Assembly in Mipot staring up (PRR in April)
6C
Tracker Peer Review, WBS 4.1.4
2
GLAST LAT Project
March 24, 2003
SSD edge bonding
Ladder assembly tool
alignment errors
100
90
Manual fast AND precise method
24 ladder assembly tools used in
parallel
Very good ladder alignment
obtained
6C
m
80
70
60
50
40
30
20
10
0
-20
-15
Tracker Peer Review, WBS 4.1.4
-10
-5
0
5
10
15
m
3
20
GLAST LAT Project
March 24, 2003
Encapsulation
Dam & Fill encapsulation
Dam Nusil 1142
Fill Nusil 15-2500
Requirements:
1. Height <0.5mm
2. Lateral overflow <0.05mm
3. Coverage of all the bondings and pads
Fast system to check
encapsulation height
6C
Tracker Peer Review, WBS 4.1.4
4
GLAST LAT Project
March 24, 2003
Ladder electrical test: methods
2 PA200 probe stations with modified chucks to
accept ladders are in activity (G&A and Mipot)
Tests:
IV curve (ladder leakage current from 0V to 200V)
CV curve (ladder total capacity and depletion
voltage)
Single channel AC test: 100 V voltage step to
measure AC insulation and AC capacity
t>to
IV,CV test scheme
t<to
Connected
strips
Interrupted
strips
AC strips test scheme
I(5t)>10nA
AC short
6C
Tracker Peer Review, WBS 4.1.4
5
GLAST LAT Project
March 24, 2003
Electrical Tests: Results
2000
1800
Leakge current history
Expected
Post-encaps.
1600
current (nA)
1400
1200
1000
800
600
400
200
Depletion voltage
0
1142
ladder ID
1163
1183
1203
1224
1244
1266
70
ladder dep. V
expected from SSD
60
50
The causes of problems 3 and 4
have been corrected,
foreseen rejection rate ∼1%
6C
40
30
20
10
90
80
70
60
50
40
30
0
20
Electrical test results:
1.
Ladder tested
251
2.
Accepted
243 (97%)
3.
Broken edge
4
4.
Probe accident
1
5.
Not understood
3
Depletion voltage (V)
Bad channels caused by bonding (coupling shorts)=0.016%
(accepted limit 1%)
No broken or bad bondings
Tracker Peer Review, WBS 4.1.4
6
150
1121
140
1101
130
1076
120
1054
110
1034
100
1014
GLAST LAT Project
March 24, 2003
Database
A Access database system
installed in the two assembly
centers, collects all the relevant
data of the ladders:
•SSDs alignment
•IV curve
•CV curve
•Bad channels (AC insulation test)
•Not bonded channels
The database allows a fast and
accurate monitoring of the ladder
production.
This database adds to the traveler
systems installed in the assembly
company (ISO9001) which ensure
the whole traceability of materials,
instruments, procedures.
6C
Tracker Peer Review, WBS 4.1.4
7
GLAST LAT Project
March 24, 2003
Conclusions
• The ladder construction successfully started (9% of the ladders have
been produced with a 97% yield, possible increase of the yield to
99%).
• Electrical and dimensional ladders characteristics well within
specifications
• Production rate > 10 ladders/day in both assembly centers that will
work in parallel (G&A Engineering and Mipot), so there are no
schedule problems with this item
6C
Tracker Peer Review, WBS 4.1.4
8