Tracker Issues Discussion with Jim Lohr
L. Klaisner (beginning of meeting)
Dick Horn (beginning of meeting)
1) Conformal Coating on connector leads negate stress relief
2) Solder on connector leads negate stress relief
4) Conformal Coat lifting
Discussion for items #1 & 2 above: Qualification MCMs which were subjected to 240 thermal cycles (-30deg. C to +85deg. C) and no units showed failure of connector leads. Qual MCMs were also subjected to GEVS vibration environment and no units showed failure of connector leads. Approx. 150-200 flight units have been subjected to 21 thermal cycles of (-30deg. C to +85deg. C) and no units showed failure of connector leads. Based on these test results, conclusion is that connector leads are reliable. Thermal variation environment of MCMs on orbit are extremely small (less than a couple degreees) compared to thermal test conditions.
Flex Cable Coupons- Discussed current status of coupon testing conducted by GSFC and Parlex. Independent lab to test coupons per Nick Virmani’s meeting notes from visit to GSFC. All flex cables that have passed GSFC coupon testing are deemed acceptable for flight. Follow-up MRB to be conducted to close and document cause and corrective actions.
Pitch Adapter Trace Cracking- Briefed Jim Lohr on current status of trace cracking and re-design of Pitch Adapter and re-qual program to be conducted.
Coupon Testing- All agreed that LAT management and LAT QE shall determine and communicate coupon testing priorities with GSFC.
1) Perform visual inspection of MCM qual units for conformal coating and solder on leads.
2) Ensure lessons learned get folded into Teledyne production to prevent recurrence of issues.
3) Update and Release LAT-DS-00898 AND -00899 Note 8 (conformal coating requirement)
4) Perform 100% inspection of MCMs for the following: (This applies to MCMs at SLAC and at INFN installed on trays for Tower A and spares).
a. Any bubble found in conformal coating which does not meet LAT-DS-00898 AND -00899 Note 8 (updated note #8) shall be reworked per documented standard rework process.
b. Inspect conformal coating for lifting around encapsulant area and around mounted components. Perform local rework to documented standared rework process. Standard rework process for conformal coating is TBD/TBR.
c. Inspect Pitch Adapters for Cracks. Record results of Pitch Adapter cracks (conductive and non-conductive) and disposition MCM by current (no greater that eight failed channels, or a single failed bias trace)
Note: For MCM inspection at INFN, record and report results of inspection. MRB will need to determine disposition for these units if they should be reworked or otherwise dispositioned. Need to determine who at INFN is to perform this inspection of Tower A MCMs. Suggested names are Aldo, Luca Latronico, and Robert Johnson (if Robert is still at INFN).
5) Supply one non-flight MCM to GSFC which has conformal coating lifted around encapsulation and also conformal coating lifted from component. Supply to Jim Lohr to hand carry to GSFC. Jim will have GSFC examine unit for possible contamination which could cause conformal coating to lift. (DONE- Albert Nguyen supplied MCM to Jim to hand carry. Documented on work-order.
6) Jerry Clinton is to contact Fred Gross (GSFC) to review conformal coating material approval status. SLAC needs a written “re-approval” for use of this material to close-out NCR generated when Fred “retracted” material approval.
7) Generate or make available “standard rework procedure” for removal of conformal coating and re-application of conformal coating. MCMs that have rework performed shall undergo electrical functional testing to verify unit functional performance.