Happy,
What is your recommendation if someone doesn't want to pay the premium price
for a manufacturer that can't hold that?
Are you an advocate for the all mask or none approach? This is the feeling
that the cost outweighs the fallout from bridging?
This isn't a trick question. I just know people that have a block of
mask clearance and others that feel that the fallout from that is to costly.
Is there a breaking value? I mean is there a pitch that you hit that almost MUST
require masking?

Chris Robertson
[log in to unmask]

  Ted,
  We typically see 0.3mm pads for 0.5mm CSPs with 0.4mm solder mask
  openings.  This is a tight spec and a lot of fabricators can't hold it,
  especially across a large panel.  If you are fortunate enough to be
  dealing with a 0.5mm staggered pitch CSP, you might be OK, but if you have
  a matrix of 0.5mm pitch pins, then you better hope that they have provided
  for unused pins because you are going to be in the 0.0025" trace and space
  realm.  If you can get out of the forest, you can use conventional vias,
  if not, then you will have to either use microvia-in-pad or a
  'near-microvia-in-pad' (called inset-vias, they are microvias as close to
  the CSP pad as possible but still covered with soldermask).  0.5mm pitch
  is a tough design if there are a lot of pins and the package design did
  not consider pcb wiring!

  Happy Holden
  Westwood Associates





  Ted Kong <[log in to unmask]>
  Sent by: TechNet <[log in to unmask]>
  12/13/2003 08:59 PM
  Please respond to "TechNet E-Mail Forum."; Please respond to Ted Kong


          To:     [log in to unmask]
          cc:
          Subject:        [TN] .5 mm pitch components


  Hi all,

  Want to find out what pad size and solder mask opening
  are people using for .5 mm pitch components?  Since
  the pad size is so small, it is a must to use solder
  mask define pads?  Are people using via-in-pads to get
  traces out or just using the outer layers?  Thanks all
  in advance.

  Ted Kong.

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