AFE Meeting, June 12, 2001

John Anderson, Fred Borcherding, Alan Bross, George Ginther,
Paul Grannis, Stefan Gruenendahl, Rick Jesik, Marvin Johnson,
Jon Kotcher, Daniel Mihalcea, Thomas Nunnemann, Paul Rubinov

1.  Sanmina progress.

    John sent an e-mail yesterday -- we don't have any later word:
    
>- Data as of 3:30 PM, Monday.
>- Approximately 58 boards made, 15 to go in right-handed run.
>- thicker paste load yielded better-but-not-great results on
>      MCMs, no shorts on other parts.  An improvement.
>- Getting approximately 50% of MCM pins to solder on pass
>  thru reflow oven.  Leftovers easy to touch up with iron.  Pattern
>       is that all pins in the two short rows are soldered, two big
>       gaps of opens along long sides.
>- Expect to see boards late this week to early next week.
>- Have asked for estimate when second batch will run, no 
>       answer yet.
>- Pads for MCMs too short for long leg of pins.  This results
>       in solder joints not acceptable under Class 2 inspection.
>       This can be fixed on new MCMs if foot of pin is made shorter.
>       Lack of solderability due to pins being too long, too easy to
>       deform.  Next MCMs should sit tighter to PC board, shorten
>       lever arm.  

    Sanmina is coping with the non-planar MCMs and pads that are too
    small as well as possible.
    John would like to have SiDet inspection and fix of open solder
    joints.  He felt however that permanent damage to the MCM or board
    due to opens was a small risk.

2.  DAB3 test stand.
    Mike Matulik ran a 1.5 day training on running the software for 3
    people.   Two of these are doing well and are now producing
    software for the test.  One improvement is the software addition
    to allow LH and RH board tests. The third student is waiting for
    an NT account.  Rick felt that the learning curve was going
    rather well.

    Modification to the test stand to allow all 8 MCM testing on RH
    and LH boards was made.  There are no further mods that are
    envisioned.  The noise level is still rather large and we will
    live with it.

    There are now 7 testers started or in the wings.  Rick feels this
    is enough to get started and see how things go and get the
    procedure ironed out.  Others have expressed willingness to jump
    in if needed.

3.  SiDet tests;
    Daniel reported the second test stand is finished (hardware) and
    hopes to have it with software tomorrow. He has 2 students, 3
    techs, plus another student coming.   He will need John A. for a
    day or so to help train and advise.

4.  AFE8 extra (the CFTstereo/CPS boards)
    John said that about 6 parts are still not in hand.  The bid for
    the assembly is not out yet, but can be done in a few days.
    However we don't yet know the input capacitance value, as we have
    not tested the modified Bd 9 with various caps installed.

    We plan to remove the Bd 9 from the platform at next access
    and take it to Lab 3 for tests.

5.  AFE8'
    John sent a note on his opinion on relayout vs. green wires:

>     "   - I'll always back relayout over adding green wires.  We can and   
> should start on this now, not later.  I assume Jim Franzen can be          
> re-hired for more layout work, and would try to get schematic entry        
> help from Pat Sheahan and/or Donna Kubik.  Donna has apparently            
> disappeared to MuCool efforts, don't know if she can be made               
> available again.                                                           
>                                                                            
>         I don't understand why there is any discussion at all on this      
> point; my opinion is that there is not enough possible calendar            
> advantage to green wires to offset the unreliability issues of green       
> wires, and it is therefore a poor risk to take.                            
>                                                                            
>         - Method of attack:                                                
>                                                                            
>                 a) obtain specific, written details of desired changes to  
> board.  Create paper copy signed by principal managers.  Once I            
> proceed to step (b), disallow any changes to document except by            
> painful formal review process which would generate further signed          
> documentation as revisions to original document.                           
>                 b) copy extant AFE-8 Revision 1C design to new AFE-8       
> Revision 2A design.                                                        
>                 c) perform exactly what is in the signed, written document,
> no more and no less.  Copy/paste schematic pieces from AFE-12              
> motherboard design as applicable.                                          
>                 d) relayout                                                
>                 e) build boards                                            
>                                                                            
> My point here is that the best way to gain calendar time is to get         
> down, in writing, exactly what everybody wants this board to be            
> and to freeze the design BEFORE any cad work is done. "                    

    Marvin emphasized the mechanical tolerances are very tight so
    green wires are tough to fit (50 mil clearance).

    We confirmed that we do not wish to make any other modifications
    on AFE8prime besides the separation of bias voltage.   We reviewed
    the inclusion of drain capacitors (needed for charge splits), and
    agreed not to put them in.  The only additional fix to the AFE8'
    would be to modify the MCM pads to allow more reliable soldering
    to the pins.

    Jim Franzen is available to start the layout.

    Marvin raised the question of baseline shifts due to dc offsets
    and current leaks to this small input cap.  We can test the effect
    with the modified board when it is removed.   Paul asked for some
    better information on the current load for preshowers as a
    function of rapidity (CPS and FPS) to help us assess this baseline
    shift problem.

6.  There was some discussion of whether to replace board 9 in the
    platform or not.  Competing uses for prototype boards are in the
    test stand training exercise.  The scribe believes the decision
    was taken not to replace board 9 for now.