Hi Steve,

I didn't know that Smart Modular Technologies was no more.  I just spec'd in
some of their DIMM's about 6 months ago.  With regard to the X-outs being
randomly placed and not machine readable, I did some work a while back for a
contract manufacturer who had just put in place a system to "fix" this
problem.  Their solution, which seemed pretty clever to me, was to place a
diamond-shaped fiducial on each board in the panel, and then, you guessed
it, have the PCB fabricator black out just the little diamond.  So rather
than a big randomly placed "X", which is great for us near-sighted humans,
you got a small paint or ink blob on the fiducial.  I don't know where on
the process line they read the diamond-shaped fiducial to tell all the
subsequent machines about the bad board locations.  But it did seem like a
really good idea (like most ideas that I don't have to implement).  Your
point about solder paste is well taken.  That one seems pretty hard to avoid
without spending more than you could save.

Regards,

Seth Goodman
Goodman Associates, LLC
tel 608.833.9933
fax 608.833.9966

  -----Original Message-----
  From: TechNet [mailto:[log in to unmask]]On Behalf Of Stephen R. Gregory
  Sent: Friday, December 21, 2001 4:20 PM
  To: [log in to unmask]
  Subject: Re: [TN] Panel Layout Standardization


  Hi Stacy!

  Having read the replies that you've recieved so far, they are giving you
good information. The only thing I can add is some past experience from my
employment at a memory company...Smart Modular Technologies, they are no
longer, was bought out by Solectron...but I digress...

  As far as X-outs, they aren't free. The FAB house won't charge you for
them, and your bare costs may be lower, but there are costs that you will
see on your production floor from X-outs.

  Normally what I see from the fab houses is a big "X" drawn on the
individual boards. That X is something that we can't program our machines to
see since it's not consistently in the same place. We normally had to sort
the panels one-by-one and put a label that the machine can see on each of
the x-outs, at a consistent location, so the machine don't try and populate
bad boards.

  The other alternative is to sort the fabs according to which boards are
bad, and then have separate programs that populate only the good
boards...either way, you still have to handle each board.

  The other thing to think about is the wasted solder paste that you print
on these bad fabs. It may seem insignificant, but when I worked at Smart
Modular, we would sometime do almost a million modules a month during our
busy times. I did a calulation of the solder paste that was wasted on bad
boards over a years time, and it was close to $50,000 a year!

  It's not only that, you need to figure in the time that's wasted in
depaneling. You say you have a router inline that depanelizes everything,
does it do only the good boards, or does it do the whole panel? Is it
wasting time routing out bad boards?

  X-out aren't a big deal in low volumes, but if you do high volumes, the
costs that you may save in the bare board costs may be insignificant
compared to what you spend on the production floor...


  -Steve Gregory-