Transcript (ppt)

GLAST LAT Project
Gamma-ray Large
Area Space
Telescope
October 1st, 2004
The encapsulation problem of the
LAT heavy trays
Alessandro Brez
INFN - Pisa
[email protected]
GLAST LAT Tracker Anomaly Resolution Team
1
GLAST LAT Project
October 1st, 2004
The tray encapsulation
DAM Nusil 1142
Fill Nusil 2502
TMCM
ladder
GLAST LAT Tracker Anomaly Resolution Team
2
GLAST LAT Project
October 1st, 2004
The problem
Lateral shift
On axis shift
On all the heavy trays, on both sides, we had bonding failures after thermo cycling.
Cause: adhesion failure of the FILL material from the ladder surface
(CTE) with subsequent induced over stress on wires
GLAST LAT Tracker Anomaly Resolution Team
3
GLAST LAT Project
October 1st, 2004
Possible solutions
We had no failures (not a single missing connection) in
the MID trays, even after 18 thermo cycles (+50,-30oC)
Something very special with heavy trays. There is no time
to model the problem or to find and test a new fill material.
The only practical solution:
NO ENCAPSULATION
The free wires are much more adaptive to CTE induced
movements (loop).
GLAST LAT Tracker Anomaly Resolution Team
4
GLAST LAT Project
October 1st, 2004
Qualification program
From EM trays:
Some EM trays have no encapsulation but
•Most of the EM ladders are from dummy wafers
•The pitch adapters of the EM TMCMs are different from
flight units
•Several bonding wires have been damaged during the
tower thermo-vacuum assembly (thermo couples placed
over the trays)
•These trays have been mounted and dismounted many
times
There are layers with a complete series of good bondings:
They survived to the tower vibe tests
They could be tested again in Centrotecnica (is it
significant? , they survived to 2 previous tests)
GLAST LAT Tracker Anomaly Resolution Team
5
GLAST LAT Project
October 1st, 2004
Thermo or thermo vacuum test
In principle we can perform a leakage current test
In climatic chamber
In thermo-vacuum chamber
test
GLAST LAT Tracker Anomaly Resolution Team
6