Leonard,

I am not aware of any guideline placing via holes in smt lands
except micro-via applications.  Any board guideline will tell you
"no via hole in smt land" Period!  Some of Ghz desingers drives
me nuts over this.  But I am in the process of designing
and testing via holes in smt lands.   I likely will use 0.38 or
0.50mm via holes located on under chip component
(off-centered) and will tent solder side via holes to prevent solder
wicking down thru them.  I know most board vendors can do
0.38mm holes with no cost increase.

regards
Matthew
NII


>>> Leonard Toohey <[log in to unmask]> February 16,
1998  2:10 pm >>>
What is the state of the industry regarding putting
vias in the center of SMT discrete device pads?

I am mainly wanting to know about 0603, 0805 and 1206
devices.
Is board thickness a factor?
What about via hole size?


Thanks,

Leonard Toohey
[log in to unmask]
12303 Technology Blvd.
Austin, TX 78727
Ph(512) 257-5423
Fx(512) 249-7236
http://www.netspeed.com

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