August 20, 2004
Tray Panel Fabrication
- The assembly vendor, Plyform, is on vacation. They will return to start mass production of bare panels at the first of September. Installation of tungsten and bias circuits is on hold, however.
- The anomaly review team for the bias-circuit/tungsten bonding issue has been formed and is scheduled to be in Italy the week of August 30.
- A new problem was found with two trays: the encapsulation needle damaged contiguous sets of wire bonds on one side of each tray. Those bonds did not fail until thermal cycled. The encapsulation process, which is very new, will be adjusted to fix this problem in subsequent assemblies.
- The Tracker team proposes to go ahead with assembly of flight Tower-A a week from now using the trays as-is. All trays would have functional MCMs mounted, but some trays would have no silicon and 4 silicon layers would be inactive due to bias shorts (these problems all result from the bias-circuit/tungsten bonding issues). The objective is to make a pass through all of the flight-hardware procedures to uncover remaining issues and to carry out at least a thermal-vacuum test with an active tower. The tower could be retrofitted with 100% active trays at a later date, TBD.
- The following items are being shipped or carried to Italy from SLAC over the coming week:
* Tower lifting fixture, already proof tested
* Tower inner shipping container, already proof tested
* Tower base-plate and cable-holding plate (for vibe test and shipping)
* Tower assembly screws and bottom-tray assembly pins
* Interface assembly hardware (cones, studs, nuts, hex bushings)
* Cable bending tool
* Solithane for fastener locking
* EGSE flex-circuit cables
- Cable-termination corner brackets are nearly done (in plating)
- 261 MCMs have been delivered to SLAC, 30 of which were manufactured with 75-ohm termination resistors.
- The Novacap capacitor issue was resolved: the MCMs manufactured with the original lot can be used as-is. The new lot will be substituted into the manufacturing when it is available.
- Bias shorts have developed in 6 completed MCMs. The shorts are internal to the PWB (NOT the capacitors), and each short affects one of 4 ladders. DPA will be done on at least 2 of the boards, and we are communicating with the manufacturer. We are also discussing how to detect the defects before MCM assembly.
- A second iteration on a redesigned pitch adapter is in progress, to solve the problem of trace cracking. The mask is now being extended all the way over the bend region, and alignment is being improved in the assembly to accommodate that and to be sure to leave adequate space for wire bonding.
- We are in the process of inspecting pitch adapters at SLAC post-burn-in, to determine whether new cracks have developed throughout the processing.