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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