1. GLAST Large Area Telescope:
Gamma-ray Large Area Space Telescope
GLAST Large Area Telescope:
Pitch Adapter PWB Metrology
Bill Craig, Charlie Young
Stanford Linear Accelerator Center

2. CMM Surface Scan Overview
6 parts were taken to LLNL for metrology
4 parts, 2 of the -05 series, 2 of the -10 series.
Several non-contact methods attempted, none were successful at getting a good view of the whole radius
Performed dense CMM scan at 1mm steps in Z, 3mm of Y travel in 115 steps, 1.5mm probe radius.
Surface data shows features on few cm length scales with amplitude of 50 to 100 microns.
No apparent difference on surface plots between the older -05 series and the newer -010 series for the few parts tested

3. Coordinate system for CMM scansZ
X=0
X=355
Serial Number
Boards were held flat by custom fixturing.
IE 176 CMM

4. Board 2100 Surface

5. Board 2146 Surface

6. Board Surface

7. Board Surface

8. CMM residuals
For each of the 4 boards, subtract a typical Y-Z plane trace from the surface.
Plot residuals to look for correlation length scales
On 3 of 4 evidence for ~10 cm length scale for variations, amplitude of 50 to 100 microns.
No apparent difference between -05 and -10 series

9. Board 2100 Residuals
Subtracted X scan [10] and smoothed with 2D 11 pixel width boxcar

10. Board 2146 Residuals

11. Board Residuals

12. Board Residuals

13. Radial profiles
For each of 355 X scans, perform four 3 point radius determination
1) Upper part of board (Teledyne side about 1/3 of the way along the arc)
2) Middle part of arc
3) Lower part of board (Italian side about 2/3 of the way along the arc)
4) Full arc

14. Board 2100 Radial Profile

15. Board 2146 Radial Profile

16. Board Radial Profile

17. Board Radial Profile

18. Radial results
The two -10 series boards look different from the -05 series boards.
The dispersion in radial measurements is lower
SLAC profilometer data seems to corroborate this
There is a decided trend in X on the lower radial measurement on the -10 series boards that is not seen on the -05 series
Limited board sample, unclear whether this has meaning but there does seem to be a significant difference.
If this were a blind study, might predict that the -05 boards would perform worse.
The very small radius toward the Italian side of the arc is worrisome but, since it seems to have been there for some time, is probably not the culprit for the sudden failure.

19. Sectioning instructions
Diane Kolos at GSFC has boards and will do sectioning and SEM analysis.
Instructions written by C. Young and sent to her on 13 January.
Status?

20. Pitch Adapter Geometry

21. Board to be sectioned at a broken trace as shown.

22. 45 degree sectioning of 1” lengths

23. Italian side CMM profile

24. Teledyne side CMM profilometery

25. Taylor-Hobson profilometery
Done on two ‘rough’ sections of the 2k series board
Worst Peak to Peak 30 microns, mean is 10 microns
Definitely periodic on few mm length scales (corresponds to tools marks visible on part under microscope)

26. Visual Inspection
Scanned ~5 boards of the 11k series that had been rejected for breaks.
Verified that breaks occurred in clumps
Few single breaks
Typical number of breaks ~>5
Several boards had many clumps of failures, these seemed to also have other hairline cracks or other signs of onset of failure
Most boards had only one or two clumps of failure, only 1 ASIC site affected.
Given the spatial distribution of irregularities in the radius may be worth doing detailed correlation between failure sites and surface features.

27. Summary No obvious visual clues from most of the profilometry
Some indication of differences in radial profile between the small number of -05 and -10 series boards profiled
More radial variation in the -05 series boards but generally flat radial profile as function of ‘X’
Indication of a significant radial variation as function of ‘X’ in -10 series boards.
No smoking guns but should correlate these findings against the spatial distribution of failures on the most recent Teledyne attempts.

28. Board 2257 Radial Profile
SLAC profilometer data.
-10 series board

29. Board 2057 Radial Profile
SLAC profilometer data.
-10 series board

30. Board 2108 Radial Profile
SLAC profilometer data.
-10 series board

31. Board 2123 Radial Profile
SLAC profilometer data.
-10 series board

32. Board Radial Profile
SLAC profilometer data.
-05 series board

33. Board Radial Profile
SLAC profilometer data.
-05 series board

34. Board Radial Profile
SLAC profilometer data.
-05 series board

35. CMM profilometry Board 2132

36. CMM profilometry Board 2108

37. CMM profilometry Board 11127

38. CMM profilometry Board 11313