Instead of a skillet I bought a cheap electric cooking plate and put
an aluminium plate on top. The temperature is controlled with an
industrial controller (thermocouple sensing on the aluminium plate). I
put the boards on only after the plate has reached stable temperature.
I tried a stencil when the board house offered it free with the PCB,
one board turned out quite good but for the second the stencil didn't
lie flat and it was a mess. I'll stick to the syringe in the pneumatic
dispenser for now. If you do more than ones and twos the stencil
probably pays off.
ST
On Fri, Jul 24, 2009 at 9:26 PM, DJ Delorie<dj@...> wrote:
>
> Henry Liu <henryjliu@...> writes:
>> Does the drop size matter?
>
> A little, but as long as they're consistent you'll be OK. It's when
> you have one big one and one little one that you risk tombstoning.
> Look for a diameter about half the size of the pad. For TQFP or TSOP
> parts, just run a bead along the pads and clean it up later with flux
> and solder wick.
>
>> Does it need to flat?
>
> No. You'll squish it down with the part anyway.
>
>> Any links to the aluminum foil method?
>
> Laminate UV film on both sides, expose, develop, etch (takes a few
> seconds). DO NOT STRIP. The thickness of two films plus the foil is
> just right for stencils and strong enough for a few boards.
>
>> I saw http://www.pololu.com/ will print mylar pretty cheap.
>
> I just used this service with good results, with 0.5mm pitch TQFPs:
> http://www.ohararp.com/Stencils.html
>
> He uses kapton instead of mylar, because the laser won't warp it.
>
>
> ------------------------------------
>
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> http://groups.yahoo.com/group/Homebrew_PCBsYahoo! Groups Links
>
>
>
>