Re: gEDA-user: dxf again

[Mark Rages <markrages@xxxxxxxxx>]

On Fri, Jul 16, 2010 at 1:35 PM, Armin Faltl <armin.faltl@xxxxxx> wrote:
> First and foremost thanks a lot!
>
> DJ Delorie wrote:
>>>
>>> I somehow feared this while I wasn't sure: so it is not posible to
>>> manually define the paste mask on a footprint?
>>>
>>
>> No.  What I do is use a perl script to create a "paste board" that has
>> all the paste apertures as element pads, but nothing else.  Then I can
>> manually edit them all, and just dump a gerber for layer 1 copper as
>> the paste gerber.
>>
>>
>>>
>>> I need this to create the footprint of a part with thermal central pad.
>>>
>>
>> Use one pad for each paste spot you need, then one overall pad with
>> the "nopaste" flag to fill in the gaps.
>>
>
> If I understand you right, this is an alternative to the "paste board"
> approach above.
> I'll go for this and provide the footprint when I'm ready.
>>>
>>> Hand-soldering is a nightmare-option with 0.5mm pad-pitch ;-)
>>>
>>
>> No it's not, I do it all the time.  Even when I use a paste stencil
>> and reflow, I often have to re-solder the pins for various reasons.
>> Just use enough flux and a big tip and it works just fine.
>>
>
> I've used the surface tension of the solder with relatively fine pitched
> square flat packs
> and "legs" with success and actual ease. The beast I'm talking about now is
> this:
>
> http://focus.ti.com/lit/ds/symlink/bq24103.pdf
>
> It has the pins beneath the package. I'll extend the pads about 0.5mm
> outside (longer
> with traces attached) as recommended, so will this trick work again?
>
> Regards, Armin
>

Oh, those (QFN-like) packages are quite easy to hand solder, except
for the thermal pad underneath.   Much easier than fragile
narrow-pitch TQFP and TSSOP parts.

If you don't need the thermal pad, just plunk the part on the board
with flux and run a solder blob around the edges.  Done.

To solder the pad underneath, you need a LITTLE paste under there and
an oven or hot air or a via underneath to put an iron on.

You will love the leadless packages if you have ever bent the pins or
solder-bridged a TSSOP part.

Regards,
Mark
markrages@gmail
-- 
Mark Rages, Engineer
Midwest Telecine LLC
markrages@xxxxxxxxxxxxxxxxxxx


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