Minutes of the Tracker Technical Meeting November 8, 2000 Hartmut said that Pisa has funds to pay for the dummy detectors, but it is not yet clear how to handle the transaction? Sandro said that they must spend these funds before December. Hartmut will contact Pisa on how to place the order. Hartmut said that he received no replies from people about needs for facsimile detectors, which will be available in fairly large quantities on the April time scale. Ronaldo said that Colin Wilburn of Micron is offering some dummies on a shorter time scale, such as January. Pisa will order a few, but they will be expensive. Hartmut said that probably 10 will be available from HPK in December. The price is likely to be about $100 each. Tom reported that he and Gwelen talked to two vendors in Southern California last week about MCM assembly and also to 1 board vendor about aramid/G10 board fabrication. Teledyne has the same wire bonders that SLAC is looking to purchase (Delvotec), and they are very interested in the job. Prices will be provided in a couple of weeks. The other assembly company was TRW. The 90 degree interconnect was something of an issue with the assembly vendors. However, the board fabricator, Young Electronics, says that they could build in a thick section along the board edge, to be machined after fabrication to make a precision radius. They are waiting on a set of drawings for both pieces before they provide prices. The material costs about 3 times what polyamide costs. Cost of the finished board is about 2 times polyamide. There was a lot of discussion of embedding converters or plating lead (for thin-converter trays) for the bias circuit. They are researching lead platers, since they do mostly tin. They are comfortable with aligning the converters to fiducials on the top of the board. Tom will send drawings to the board vendor to get estimates. Tom talked about tray fabrication vendors. He will go to talk to PCI and Alcomp tomorrow with Hytec. There is a 3rd vendor in Texas with experience in carbon-carbon that Tom would like to talk to. He would like to encourage competition at this stage to avoid problems with sole-sourcing from SLAC later, when we go into production. If we let the market compete now, then there is a better chance of sole-sourcing the production to the same company that did the prototyping (assuming that that works out well). Sandro said that they have been talking to Italian factories that can make trays and do ladder assembly. They have a first answer from a vendor, to make mockup trays at $600/tray including attachment of tungsten squares (with 100um alignment) and bias circuit. It is the same producer as for the Agile trays. The price does not include the material costs of the face sheets and closeout. He would like a drawing of the closeout design. Tom said that we are getting close to a preliminary drawing for the closeout. We still need to include the new dimensions, as they have changed in the last week. In a couple of weeks it should be ready for distribution. Ronaldo said that they are still waiting for a quote from a second vendor. Tom reported on the decision from the Tuesday IDT meeting. Dimensions were changed to accommodate IPC rules on spacing from the 150V electrodes, to facilitate rework during I&T, and to improve cable clearance through the grid (around heat pipes) and between the calorimeter and grid. The bottom line is that the gap between towers increased by 0.5mm, and the trays are 1 mm larger in both transverse dimensions. Ossie said that they reran the thermal test on baby-detector ladders at SLAC. An interesting problem occurred with the current measurement at low temperature: frost buildup dominated the leakage current. However, there were no mechanical failures during about 3 cycles from –50C to +60C. They obtained repeatable strain measurements, but in general the strain was small. They did not see lock-in of strain at high end. They will send raw data and comments as well as reduced data to Gwelen. He would like to run again the low end with an N2 purge to get rid of frost.. Ossie reported on talks that he has had with manufacturers of solar panels about adhesives for silicon attachment. His write-up can be found on the UCSC Tracker mechanical web page. Engineers and adhesive experts uniformly said that while they used epoxy 20 years ago, it is never used now. Everybody uses silicone. Creep and precision were discussed. Our test range is well within the material's elastic range, so there should be no creep. Industry generally uses these adhesive for CTE and vibration decoupling. They use 5 to 8 mils for optimum performance. Epoxy long term performance, on the other hand, is poor. It loses polymers and turns chalky. Conductive silicones need fibers or angular irregular grains, so that the conductive grains don't pull apart with a rise in temperature. About 40lbs/square inch is sometimes used for clamping. That could be much less with good control of adhesive drops. Industry places wafers with 20um gaps and has no problem with the adhesives with that high precision. Ossie said that the silicone adhesive recommended by Lockheed is readily available. Sandro would like a sample. The Perugia group has instruments in Terni to qualify adhesives. They can study stability in thermal cycling and also do shear tests versus temperature. Sandro said that the 2-D thermal analysis at Pisa is done. The results confirm Roman's analysis. They find that in thin layers the mechanical properties of the adhesives do not change significantly the stress in the silicon. He has put on their web page the names of 3 adhesives used at CERN for radiation up to 5 Mrad. Ossie said that in his note is the name of someone at Lockheed who can do adhesive testing. The recommended adhesive has 20 years of experience with solar cells. Guido said that he likes the idea of following recommendations from the solar panel industry. Ossie will obtain samples of the adhesive. Sandro will send a note on how much they need. Ossie will send literature on the adhesive to Sandro. Ossie will start defining new test structures, using this adhesive. He wants to start with a simple test of silicon on metal. Tom said that he will ensure that we get parts for the eventual test structures that are faithful to our design, including aramid samples. Nick reported that they installed a new controller chip, which seems to work. Still they don't see any data coming from the front end. He will call Wilko. Sandro said that they have two pages on their web site of a summary of opinions on glues and mockups. He will also put there the results of the 2-D thermal analysis. Decisions: 1. Increase the gap between towers by 0.5 mm. 2. Increase the tray lateral dimensions by 1.0 mm. Action Items: 1. BJ: send out again the list of dimensions, which correspond to the recent decisions. 2. Hartmut: contact Pisa to figure out how to place the order for dummy detectors. 3. Tom: send drawings to the board vendor to obtain estimates. 4. Tom: distribute drawings of the closeout design when updated with new dimensions. 5. Ossie: send thermal-test results to Gwelen. 6. Ossie: obtain samples of silicone adhesive, as recommended by Lockheed. 7. Sandro: send a note to Ossie on how much adhesive they need.