We had a meeting today
Present: Jim Lohr, Tracy Sheppard, Tavi Alvarez, Jerry
Clinton, Dave Rich, Tom Himel and near the end Diane Kolos came in.
Action items:
Rich: Bring the 3 boards which failed the
leakage current test at Teledyne back to SLAC from Teledyne (they are SN610,
11275, 11505)
Rich: Send SN 11505 to Diane Kolos at Goddard to
use thermal imaging to locate the problem and then section or plane the board
to find the root cause.
Himel: Send Kolos information about what to
power. Also, discuss with her and other
Goddard personnel of her choosing exactly how to examine the board.
Himel: Double check with Don Knaepple about other
boards that were flakey (had behaviour change when pressing on part of the
board.) [done:
I had miss understood Don. There is only one such board (SN 11508) and it
presently resides in Himel's office.]
Kolos: Will email Himel (tmh@slac.stanford.edu) an
example coupon analysis and a picture or two. This is just so he can see
exactly what is checked.
Himel: This wasn't decided at the meeting, but he
will get a bad bare board, and have the weight loss checked as a function of
bake time at 125 degrees C. This will
help us determine how long to have Teledyne bake the boards.
Minutes:
Tom Himel was asked to spend
15 minutes summarizing the problem. He
did an excellent job ;) taking only 75 minutes. This dominated the time of the
meeting. All the information discussed
was in the document that was previously distributed so is not repeated here.
We will plan to start having Teledyne bake the
boards before reflow. Parameters will be
determined by some of the actions items above.
We will use 120-125 degrees C if the boards can take it as that is what
Arlon (the prepreg manufacturer) recommends.
Otherwise we may fall back to 93 degrees C, the normal NASA spec. We plan to do this not because we are sure it
will help, but because it may help (multiple people recommend it) and we don't
think it will do any harm and it shouldn't be too expensive.
We will get bad boards from
Teledyne and have Goddard study one.
Note that these may not have the same failure mechanism as the ones that
fail in burn-in, but maybe we will learn something interesting.