Minutes of the Tracker Technical Meeting
February 20, 2003
1. Robert: talk to Teledyne about the soldering problems
2. Erik: look into what is needed for good thermal transfer from MCM to closeout
3. Robert: check whether the MCM plated through screw holes are grounded
4. Tom: bring back carbon-carbon bars and facesheet sample
5. Tom: add to the sidewall order enough for the static load fixture
Sandro reported several problems with the mini-tower MCMs:
1. The trimming of pitch adapter at the ends is sometimes not sufficient, such that the MCM is too long for the space between closeout cornerposts.
2. The gluing of the pitch adapter is sometimes incomplete along the edge where G&A must wirebond. Tom said that we will add a test or inspection step at Teledyne for this edge.
3. There was a soldering problem on at least one MCM. A capacitor that was bumped slightly broke off. Sandro said that the soldering in general did not look good. Robert will take this up with Teledyne (more information and photos are needed).
4. The double-sided transfer adhesive did not work well for mounting the MCM to the tray. Too much pressure is needed to make it adhere, and in any case it doesn't seem possible to work out all of the air bubbles. The screws cannot hold the MCM flat, and there is a danger of overtorquing them and tearing out the threads. Sandro suggested using instead the same epoxy as used for edge-bonding SSDs. A clamp will be required during the curing. Some epoxy can be put on the screw threads to keep them from backing out. The MCMs will be attached to the tray and wire bonded to the pitch adapter and competely tested before committing SSD ladders to the tray. Sandro suggested a long bead of adhesive under the line of ASICs and under the connectors, with maybe some dots elsewhere, to prevent trapping of air. Erik will consider what is needed for thermal transfer.
Sandro asked if the plated through screw holes in the MCM are connected to ground. They do not appear to be to him, but they should be. Robert will check on this.
Sandro reported that 2 trays of the mini-tower are at Pisa. They are working on setting them up to detect particles from a source. At the beginning of next week the last tray will be wire bonded at G&A.
7 flight ladders from the first lot of 300 still to be encapsulated and tested.
Tom said that at Plyform today they discussed sidewall material at Plyform. They will continue tomorrow. A COI representative was there.
Tom will bring back a sample of facesheet material for outgassing tests.
Only two more EM trays need tungsten bonded to them.
Top tray status: the tooling still is at Pisa waiting to be measured.
BJ will finish designing and procuring bars for the bottom-tray panel assembly fixture. The height is the critical new dimension, plus how it interfaces with the facesheets. Hytec first needs to verify that they did not change the core thickness in their design work.
Erik said that the gap from bottom tray closeout to grid should be 4.5mm now.
They will finalize these details and then BJ will complete the bottom-tray assembly drawings.
Tom will pick up 4 bars of carbon-carbon for the EM bottom closeout at Pisa and bring them back.
Erik said that the K13d volume fraction in the sidewalls needs to be reduced from 60% to 50%. This will cause a 20% impact on the tower delta-T. Stiffness will be a little reduced, also, but that is not an issue. Hytec is putting this into the model.
Erik reminded us that he needs 4 short sidewalls for the static test fixture. About 2 walls cut in half should do. Tom will add this to the order. The material purchase already is for enough for 8 walls.
Erik reported that the flexure design problem was solved. 12% is now the worst case, even at 45g. To accomplish this they had to change the whole design of the blades.
Hytec will do sidewall tests this week.
COI will lay up the EM closeout pieces. We still need to decide where to machine them.