Hi Daan,

With a 12 mil pad size, it only leaves a 15.8 mils
diagonal spacing for the interstitial pad, resulting a
pad size of 10-12 mils.  It is not possible for
drilling.  By ordinary via, do you mean micro vias?

Ted
--- "d. terstegge" <[log in to unmask]>
wrote:
> Hi Ted,
>
> Padsizes you can find in IPC-SM-782 or IPC's online
> footprint
> calculator. 12 mil width is standard, anything
> smaller than that may
> result in problems with paste printing. This leaves
> hardly any space for
> a good solder mask stripe, therefore it is quite
> common to have one
> large soldermask window around each row of pads,
> although some would
> argue that you need soldermask between each
> individual pad to get good
> gasketing of the stencil while printing solder
> paste. You may need the
> inner layers for the fan-out pattern, but that
> doesn't mean you need
> via-in-pad. When possible use ordinary via's for
> this.
> Hope this helps.
>
> Daan Terstegge
> Thales Communications
> Unclassified mail
> Personal Website: http://www.smtinfo.net
>
> >>> [log in to unmask] 12/14/03 02:59am >>>
> 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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