Minutes of the MCM Assembly Meeting at Teledyne

August 15, 2002


Action Items:

  1. Teledyne will send to UCSC a sample of the conformal coating material, to be used in qualification testing of the polyswitches.
  2. UCSC will send to Teledyne the graph of recommended soldering temperature profile for the polyswitches.  (done)
  3. Teledyne will send UCSC their present temperature profile for reflow soldering, to used in the MCM qualification testing.  (done)
  4. Teledyne will review their reflow soldering procedure to try to minimize the temperature.
  5. Teledyne will review their cure schedule for die attach to try to stay at a low enough temperature for the polyswitches.  They will send UCSC information on the temperature and duration, to be used for polyswitch qualification testing.
  6. SLAC will modify the MCM layout to provide adequate clearance for parts placement around the encapsulation dam place around the second screws from the MCM left end.
  7. Teledyne will send SLAC information on which 4 parts had bad, kinked tapes that clogged up the pick-and-place machine.  (done)
  8. SLAC will send new reels of those four parts.  (done)
  9. SLAC will send Teledyne information on the vendor for the connector attachment screws.  (done)
  10. SLAC will review the length of the screws for connector attachment.  (done)
  11. SLAC will obtain some pan-head screws for connector attachment for possible alternative use.  (not needed)
  12. Teledyne will counterbore the backs of the PWBs for the connector attachment screws.  (done)
  13. SLAC will correct the MCM drawings to include the counterbore.  (done)
  14. SLAC will revise the pitch adapter flex circuit layout to
    1. make the tabs between ICs narrower
    2. move back the coverlayer on the IC side to ensure at least 8 mils bonding area after considering all tolerances
    3. increase the trace length on the SSD side, to ensure that the traces always get cut off to the edge when trimming following flex circuit bonding (note: a bus bar could be considered on this end for the gold plating.
  15. Teledyne will review the bonding procedure for the pitch adapter flex circuit to ensure slight positive squeezout of the adhesive
  16. Teledyne will send by email their set of photographs of the problem areas.  (done)
  17. Teledyne will rework the existing 2 test pieces to fill in the epoxy voids and then will send them to SLAC (to be forwarded to Pisa).  (done)
  18. SLAC/UCSC will create official parts numbers for the ASICs.  (done)
  19. UCSC will ship a few new untested GTRC asap to Brian to be used for programming.
  20. SLAC will create and send to Teledyne better documentation for the assembly with separate documentation for the thermal models (long and short) versus functional modules:
    1. MCM assembly drawings
    2. parts list, taking care of all questions sent by Teledyne (urgent!)
    3. updated purchase order, including delivery dates.
  21. SLAC will send Teledyne two more boxes of MCM shipping containers.
  22. UCSC will install a modem in the test-station computer (if it doesn’t already have one).



  1. The encapsulation cup around the second screws from the left overlaps the keepout area for at least one part, thus interfering with the pick-and-place machine.
  2. Some of the parts reels sent by SLAC were damaged.  The tapes were kinked, causing the cover tape to come loose prematurely, letting parts jump out jamming the pick-and-place machine.
  3. The PWB is getting bowed slightly when the connectors are bolted on, producing uneven clearance for the solder pads.  This occurs because the hole spacing is slightly off, and the flat head screws try to center in the holes.  Also, the countersink is missing in the PWB, so the screw head sticks out and interferes with everything.  In addition, the screws appear to be too long, even with no countersink, and may interfere with the sidewall.
  4. The board bows when the ICs are attached.  This causes problems in wire bonding, as there is significant bowing even between successive screws holding the board down.  There are a couple of issues here:
    1. The board can be wire bonded by holding it down with vacuum, but this requires the board to be removed from the assembly fixture.  There was a suggestion to drill vacuum holes in the assembly fixture so that both it and vacuum could be used simultaneously.
    2. The bending may be caused by the high (165C) cure temperature for the die attach adhesive.
    3. This brought up the issue that 165C is probably too high for the polyswitches, so a lower temperature cure needs to be investigated in any case.  The polyswitch maximum operating temperature is 85C.  It wasn’t clear whether they could withstand somewhat higher temperature for a few hours.
  5. There are some problems with the pitch adapter flex circuit:
    1. The cover-layer tabs between ICs, which are needed to keep the coverlayer in alignment, sometimes overlap the first trace on one side or the other, leaving little room for wire bonding.
    2. The wire bonding area on the IC side tends to get smaller and smaller toward one end of the board, from a combination of tolerances in the layup of the circuit and in the mounting onto the PWB.
    3. The traces on the SSD side are not long enough and don’t always come to the edge of the board, reducing the wire bonding area on that side.  They should be extra long so that they get trimmed off flush.  It was noted that they could be made extra long and connected to a buss bar, which would make it easy to gold plate the circuit at the end, instead of using a “gold-body” technique.
    4. The adhesive for bonding the flex pulled in from the edge, especially along the SSD side.  This would give poor wire bonding support for the work in Italy.  This may be resolved by increasing the amount of adhesive applied, to ensure a small fillet from squeeze-out.
  6. The documentation sent so far by SLAC is not clear, is incomplete, and needs to be improved.


Other notes:

1.      Teledyne has tested the pick-and-place assembly.  They are using an IR reflow for soldering, with the board still mounted on the carrier (which has significant heat capacity).  They are setting up to dispense solder paste with an Asymtek machine, for which they have a special solder-paste dispensing head (the machine is usually used for gluing).

2.      They found out the hard way that one of their two flux cleaning solutions attacks the acrylic adhesive in the flex circuit.

3.      Teledyne modified a screen printer to apply adhesive to the flex circuit through a stencil.

4.      They are getting good bond pull strength:

a.       Chip to PWB: 8.5 g mean, CPK 4.8

b.      Chip to Kapton: 9.5 g mean, CPK 2.4

5.      UCSC will supply tested ICs to Teledyne by about the end of the first week of September.

6.      Mutsumi Sugizaki (Japanese national) and Zhigang Wang (Chinese national) will go to Teledyne with the test system when the first live MCM has been wire bonded.  It will comprise one rack of electronics.  A single table will be needed at Teledyne for workspace, plus floor space for the rack.  An analog phone line may be needed for modem connection.

7.      The production plan now is

a.       41 short thermal-model boards by 9-15

b.      4 long thermal-model boards by 9-15

c.       13 live boards by 9-30