From: Marsh, Darren S. [marsh@SLAC.Stanford.EDU]
Sent: Tuesday, April 22, 2003 3:11 PM
Subject: Summary of Tracker Ladder Production Readiness Review
A Tracker Ladder Production Readiness Review (PRR) was held on April 16, 2003, at Mipot S.P.A. (http://www.mipot.com/). The purpose of the PRR was to show that the ladder assembly will meet the final performance and design specifications.
The following individuals were participants in the PRR.
Darren Marsh - LAT Mission Assurance - Committee Chair
Tom Borden, LAT Tracker System Engineer
Alessandro Brez, INFN Development Engineer
Robert Terpin, Mipot Technical R&D Director
Eva Neiner, Mipot Quality Assurance
Pietro Bresciani, Mipot Senior Engineer
Completion of the PRR and resolution of all resulting action items constitutes readiness for flight production.
The subject Tracker Ladder Production Readiness Review (PRR) is for product manufactured at Mipot S.P.A. in Cormons, Italy. A total of 800-1000 Tracker ladders will be manufactured at Mipot. The total number of ladders manufactured at Mipot will be determined upon execution of the follow-on contract to the first order of 100 ladders.
Links for all relevant ladder production documentation can be obtained at:
The following issues were addressed as part of the ladder PRR and action items are noted.
1. 10 flight quality ladders were manufactured subsequent to completion of ladder process development activities. The test result summary for these 10 ladders is attached. All 10 ladders produced results that met specification requirements. There was a brief discussion on the post-encapsulation leakage current on ladder #3004 which was higher (but well within specification requirements) than the balance of the production lot. There was agreement this leakage current measurement was in all liklehood, due to a variation in the amount of time after encapsulation the ladder was tested. It was recommended the leakage current be retested on this ladder.
It was also suggested efforts to improve the dead channel attribute would be beneficial to the Tracker program. Specifically, it was identified improvement on the probe station measurement activity be investigated.
The Mipot production traveler for the first 10 flight quality ladders was reviewed and found to be thorough and complete. In addition, a visual inspection of ladder bonds on a sampling basis by LAT personnel was performed with no adverse observations identified. It was noted a failed bond was identified on ladder 3000 (acceptable per MIL-STD-883) but it was not noted on the production traveler. The LAT representatives requested all ladder abnormalities be documented for informational purposes.
2. The Mipot Ladder Assembly Quality Plan, PQ02.03, was reviewed and discussed in detail. The plan was determined to be complete and concise. It was recommended the plan incorporate a reference to the LAT Tracker Ladder Assembly Procedure.
3. Mipot was reminded that no process changes are allowed without the approval of the INFN Technical Lead.
4. A test correlation was performed by INFN on 4 ladders (G&A ladders) between test equipment located at INFN, Mipot and G&A Engineering. The results of this correlation study indicated there was no statistical measurement difference between ladder equipment test set-ups at the various locations.
5. A database is planned to be implemented to capture pertinent inspection and fabrication data for the ladders manufactured at Mipot. The database will be implemented by INFN personnel in conjunction with the production of the next 90 ladders. It is understood the database will supplement the Mipot internal process traveler system and not replace it. It should be noted the database is web based and will be accessible to all LAT personnel.
6. Presently, leakage current is performed by INFN personnel. The plan is for INFN to transfer the responsibility for this test to Mipot prior to the follow-on contract. INFN regongizes the importance of providing adequate training to Mipot personnel to perform this activity.
Authorization to proceed with flight production of the Tracker Ladder production at Mipot is granted based on the results of the PRR performed. Additionally, it was determined the first 10 production ladders manufactured are flight quality ladders and usable as such.
Darren S. Marsh
GLAST Large Area Telescope Project
Stanford Linear Accelerator Center
2575 Sand Hill Road, M/S 43A
Menlo Park, CA 94025