- The problem with encapsulation of wire bonds between MCMs and SSD ladders is more serious than realized last week. It is a thermal-cycling effect that is breaking to bond between the encapsulation fill material and the dam and silicon surface. When the encapsulation comes loose it breaks the wire bonds. This has only been observed on trays with thick tungsten. Remedies are under study, including consideration of eliminating the encapsulation of these wire bonds (the encapsulation appears to be a bigger risk than a benefit, and the process is difficult and time consuming).
Several trays, some with silicon, some without, were
put into the thermal chamber in
Stacked Tray Testing
A stack of 10 trays with 19 layers of live silicon is
286 MCMs have been delivered to SLAC. Shipping burned-in MCMs to
- DPA and ultrasound is being done on two MCMs with internal bias shorts to try to understand better the failure mode. The team is considering a higher voltage test of these nodes prior to MCM assembly to weed out any defective boards.
- 17 MCMs were carefully inspected for cracks in pitch adapters following burn-in. Of all the cracked-trace candidates found, only a few measured to be nonconductive. A set of MCMs was inspected and will go into 200 thermal cycles to investigate possible crack formation. Work continues on procuring new pitch adapters without any nickel plating in the bend region, to eliminate cracking.
Flex Circuit Cables
- Several of the flight cable panels failed coupon testing, due to incomplete connection between plating of the vias and the internal planes. A LAT delegation is visiting Parlex today to deal with this serious issue.
SLAC Deliveries to
- Several shipments are going out this week and early next week, including the lifting fixture, vibration fixture, inner shipping container, cable-holding frame, and EGSE systems.
The interface hardware will be hand carried to
The last items for Tower-A
assembly, the cable-fixation corner brackets, are finished and should ship to
- Procurement of the shipping container has been held up in purchasing, which would be a problem if Tower-A were not delayed.