Minutes of the MCM Assembly Meeting at Teledyne
August 15, 2002
will send to UCSC a sample of the conformal coating material, to be used
in qualification testing of the polyswitches.
will send to Teledyne the graph of recommended soldering temperature
profile for the polyswitches. (done)
will send UCSC their present temperature profile for reflow soldering, to
used in the MCM qualification testing. (done)
will review their reflow soldering procedure to try to minimize the temperature.
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.
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.
will send SLAC information on which 4 parts had bad, kinked tapes that
clogged up the pick-and-place machine. (done)
will send new reels of those four parts. (done)
will send Teledyne information on the vendor for the connector attachment
will review the length of the screws for connector attachment. (done)
will obtain some pan-head screws for connector attachment for possible
alternative use. (not needed)
will counterbore the backs of the PWBs for the connector attachment
will correct the MCM drawings to include the counterbore. (done)
will revise the pitch adapter flex circuit layout to
the tabs between ICs narrower
back the coverlayer on the IC side to ensure at least 8 mils bonding area
after considering all tolerances
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.
will review the bonding procedure for the pitch adapter flex circuit to
ensure slight positive squeezout of the adhesive
will send by email their set of photographs of the problem areas. (done)
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)
will create official parts numbers for the ASICs. (done)
will ship a few new untested GTRC asap to Brian to be used for
will create and send to Teledyne better documentation for the assembly
with separate documentation for the thermal models (long and short) versus
- MCM assembly
list, taking care of all questions sent by Teledyne (urgent!)
purchase order, including delivery dates.
will send Teledyne two more boxes of MCM shipping containers.
will install a modem in the test-station computer (if it doesn’t already
encapsulation cup around the second screws from the left overlaps the
keepout area for at least one part, thus interfering with the
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.
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.
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:
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
bending may be caused by the high (165C) cure temperature for the die
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
are some problems with the pitch adapter flex circuit:
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.
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.
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.
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.
documentation sent so far by SLAC is not clear, is incomplete, and needs
to be improved.
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).
They found out the hard way that one of their two flux
cleaning solutions attacks the acrylic adhesive in the flex circuit.
Teledyne modified a screen printer to apply adhesive to the
flex circuit through a stencil.
They are getting good bond pull strength:
Chip to PWB: 8.5 g mean, CPK 4.8
Chip to Kapton: 9.5 g mean, CPK 2.4
UCSC will supply tested ICs to Teledyne by about the end of
the first week of September.
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
The production plan now is
41 short thermal-model boards by 9-15
4 long thermal-model boards by 9-15
13 live boards by 9-30