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 bcraig@slac.stanford.edu 650-926-2983

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

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

Board 2100 Surface

Board 2146 Surface

Board 11312 Surface

Board 11314 Surface

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

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

Board 2146 Residuals

Board 11312 Residuals

Board 11314 Residuals

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

Board 2100 Radial Profile

Board 2146 Radial Profile

Board 11312 Radial Profile

Board 11314 Radial Profile

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.

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?

Pitch Adapter Geometry

Board to be sectioned at a broken trace as shown.

45 degree sectioning of 1” lengths

Italian side CMM profile

Teledyne side CMM profilometery

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)

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.

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.

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

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

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

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

Board 11127 Radial Profile SLAC profilometer data. -05 series board

Board 11313 Radial Profile SLAC profilometer data. -05 series board

Board 11317 Radial Profile SLAC profilometer data. -05 series board

CMM profilometry Board 2132

CMM profilometry Board 2108

CMM profilometry Board 11127

CMM profilometry Board 11313