Re: gEDA-user: Using SMT

[Dylan Smith <dyls@xxxxxxxxxx>]

On Tue, 24 Jun 2008, Robert Butts wrote:

> I'm about to start bread boarding a desin.  I have a few surface mount chips
> that I got SMT-to-DIP adapters for.  I also purchased SMT paste.  I have
> never worked with surface mount devices.  How do you paste the chip to its
> footprint?

It's very simple. Just run a bead of paste down the pads. For larger SMT
stuff like SOIC, the solder mask on the PCB will mean the paste will all
migrate to the pads when it's heated, leaving you with neat joints. For
fine pitch stuff, you may get some briges (jumpers). It's easy to get too
much paste on! But you clean that up with desoldering wick and a soldering
iron once you've done the reflow soldering.

I bought mine in a syringe with a fine pointed applicator. I do it a bit
like these guys:

http://www.curiousinventor.com/guides/Surface_Mount_Soldering/Solder_Paste_and_Toaster_Oven

Except that I use a hot air gun rather than an oven. My hot air gun is
*not* fancy, it's actually from the hardware store. On its low setting it
doesn't blow too hard (so I can solder little 0603 parts with it) and it
gets to just the right temperature for reflow soldering.


> you get the excess, if any,
> paste out?  I have a feeling > it's got something to do with heating it.

I don't worry about excess until after I've hot-air'd the board, I then
just use a soldering iron and solder wick to suck up any excess.



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