Depends on whose padstacks you use. We use minimal pads and have 300u (12
mil) between the copper of the pads under the 0402 (1005 metric). That
leaves a solder mask web of 200u (8 mil) so if you have a 50u (2 mil)
tolerance in your solder mask, a 100u (4 mil) trace will go under the
component using 4/4 design rules.

I don't do that unless I absolutely have to because of the slight
possibility of having an exposed trace if the solder mask registration is
out of spec, but I have done it and it has worked. In volumes too - some of
our modules ship in the 100k units per month.

I don't know of any formal spec forbidding this, but hey, at the sharp end
of design we push the boundaries. We make our own rules in conjunction with
fab and assembly guys and gals. These are your very best friends - they'll
make you look good and you'll make their job easier.

Cheers........
 
Andy K
SyChip Inc

Phone   Within Australia 02 9499 4853
            International  +62 2 9499 4853

-----Original Message-----
From: DesignerCouncil [mailto:[log in to unmask]] On Behalf Of Tempea,
Ioan
Sent: 2007-02-17 00:40
To: [log in to unmask]
Subject: Re: [DC] Traces between 0402 pads

> Dear colleagues,
> 
> is there any standard saying that traces should not be routed between 0402
pads, i.e. under the component? I have a serious discussion and really need
to back it up with a formal document.
> 
> Thanks,
> 
> Ioan

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