Re: gEDA-user: Anybody had luck with QFN64 at PCBExpress et al?

[Steve Meier <smeier@xxxxxxxxxxxxxxxxxxx>]

The shop I use insists that the solder mask features must be at least 5
mills wide other wise you should gang unmask the pads.

Steve Meier

joe tarantino wrote:
>
>
> On Feb 2, 2008 11:23 AM, Jeffrey Baker <jwbaker@xxxxxxxxx
> <mailto:jwbaker@xxxxxxxxx>> wrote:
>
>     Nearly every major part I need for my latest project is packaged
>     in a QFN (or LFCSP as they call it over at Analog Devices).  I'm
>     worried because the parts have round leads and Sunstone, the PCB
>     prototype shop, says they can't make radiused SMD pads.  Has
>     anyone run into trouble with this, or are square pads OK?
>
>     Generally speaking the .5mm-pitch QFN seems to be on the edge of
>     or beyond the capabilities of a proto shop like Sunstone, but
>     Sunstone has the best tolerances I've been able to find.
>
>     -jwb
>
>
>
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>
> I have had one of the Sunstone shops build boards with QFN32 and QFN48
> as I recall.  Results were pretty good.  They had square-ended pads.
>
> -Be careful of solder resist "floaters" due to the little pieces
> between the leads.  Best bet is to remove all resist between pads.
> -You may want to check your gerber files to see how much solder paste
> will be applied and check with Sunstone to see if it is sufficient (or
> too much).
>
> Does your pad have a large heat sink pad on the back?  If so, you must
> carefully construct this pad in the footprint (possibly out of
> multiple squares).  Again, check the paste layer.
>
> Joe T
>
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