- About 1300 ladders with good IV curves are complete (about 9 towers)
- 248 more are ready for electrical testing
- 260 are in fabrication
Bias Circuits: 571 out of 850 delivered by Parlex.
- There have still been some problems with voids in the adhesive bonding of bias circuits, but these remaining problems are not related to the tungsten. Process improvements were introduced at Plyform that greatly reduced the incidence of unacceptably large bubbles.
- Etching and priming of tungsten tiles is going well at Plyform.
- Tray assembly at G&A was halted this week pending arrival of new MCMs from SLAC, because a tray was found to have about 300 disconnected channels in the MCM on one side (see below).
Plyform has agreed to pay the bond to get the prepreg
out of customs in
SLAC will send the final prepreg shipment to
- Conformal-coating rework was done this week on >40 MCMs.
- The pitch-adapter electronic test fixture finally is now working and has been put into the production flow. It tests all of the connections to the 1536 input channels through the pitch adapter and wire bonds and works efficiently with very solid results (only occasionally a few false negatives). Hand probing is still used to test the 16 bias traces.
- The problem of 300 disconnected channels within 1 MCM was studied. Using the new test fixture, one nonflight MCM was found at SLAC with up to 80 disconnected channels. Some of the connections were intermittent, depending on how much pressure was applied to the edge of the board. The problem was isolated to the wire bond connections to the pitch adapter with some confidence. Out of 42 flight MCMs tested yesterday and today at SLAC, 1 had 151 disconnected channels and all others had no more than 8 (average less than 2 per MCM, with most of those due to known cracked pitch-adapter traces). Plans are being made to study and hopefully improve the controls at Teledyne for the wire bonds to the pitch adapter.
The 41 good, fully tested MCMs will be hand carried to
- More news on the cause of bias short circuits on some MCMs: DPA at GSFC found a fleck of metal at the location of the short between layers 7 and 8.
- Teledyne is still not back online, but some progress was made on getting a quote from Teledyne for the process modifications needed. Studies are in progress to understand better the cause of conformal coating contamination of the connectors.
Flex Circuit Cables
- Tracker and QA representatives are at Parlex this week to try to resolve QA and schedule issues.
- Some bad coupons are being found still in the new process. We do not have a set of cables for Tower A that we can have full confidence in. A plan is being put together to do testing on some existing cables to evaluate the risk of using for flight some of the cables that we have now (including the rare cables with all good coupons).
- Work proceeds on getting prototype cables from two new vendors, one of the two cases being long cables spliced from pairs of shorter cables.