[hpsdr] SMT Soldering and Circuit Board Heat Question

[Cecil Bayona]

The actual temperature recommended is 425, but it's there for a few seconds 
only, the whole process takes about 90 seconds with fairly controlled 
temperature profile.

Nothing can be rubbing or touching the components or they will move off the 
pads, once the solder melt the only thing that holds the components is the 
surface tension of the solder.

On Monday 07 August 2006 19:07, David Toepfer wrote:
> ***** High Performance Software Defined Radio Discussion List *****
>
> QUESTION:
>
> Since you say the point is to head the board up to 100C (212 deg F), can't
> one simply stick the board in a sealed bag (suck out most air you can) and
> drop it in a pot of boioling water?  Boiling water never get's hotter than
> 100C.  Some simple trial/error should be able to determine how long of a
> boil boards of specific material and size.  Seems cheaper.  No hot plates,
> ovens, or thermometers to buy either.
>
> dt
> .
>
> --- Bob Fish K6GGO <rwfish at comcast.net> wrote:
> > ***** High Performance Software Defined Radio Discussion List *****
> >
> > Hi Bruce,
> > The hot plate is only to bring the board and the parts on it up to an
> > idle temperature of about 100deg C. (212 Deg F). No hotter than that.
> > The board and parts can stay at that temp all day without damage. The
> > temperature profile that the manufacteurs use in the big reflow ovens
> > goes like this; the temperature ramps up to 100 degrees C (your hot
> > plate temperature) and stays there for 3 or 4 minutes. This is to
> > achieve thermal stability and to let the solder paste outgas a little
> > bit, then it continues to ramp up to around 200 degrees C (this is where
> > the solder melts) but does not stay there, it imediately cools down to
> > room temperature.
> > To simulate this profile with the tools you have, all you have to do is
> > put the solder paste on the pads where the parts go and this is the big
> > secret to success: use way less paste than you think you will need. On
> > the fine pitch parts all you really want is a sweat joint, other wise
> > they will bulge over and short to the adjacent pin. After you place the
> > parts in the paste, place the board on the hot plate and bring it up to
> > 100C (220F) let it soak there for 3 or 4 minutes, then with the board
> > still on the hot plate at 100C use the heat gun on the board with a
> > waving motion until the solder paste turns from dull gray to a shiny
> > silver in color. It may not happen to the whole board at once,
> > especially if it is a large board, but once it does your done. Turn off
> > the hot plate and heat gun and let the whole works cool down to room
> > temperature. The higher teperature is where damage could occur if left
> > there for too long. So, once the paste turns shiny silver take the heat
> > gun away. By the way, you can do two sided boards if you put small metal
> > stand offs on the board and let the previously soldered parts hang
> > upside down while you do the other side. They just reflow again.
> > I was a little worried when I first tried it also, But it works great
> > with a little practice you will be a Pro. Just make sure you keep the
> > hot plate at 100C and no hotter. The parts can stay at that temp all
> > day. Just use the heat gun to briefly heat the paste to melting temp.
> > Good Luck! Let me know how it went!
> >
> >
> > Bob   K6GGO
> >
> > Bruce K3CMZ wrote:
> > >***** High Performance Software Defined Radio Discussion List *****
> > >
> > >
> > > I have been trying to learn how to solder these smt parts.
> > >
> > >What I have is some solder paste with a melting temp of
> > >361 degrees F, and a cheap six inch hot plate. The hot
> > >plate is made out of cast iron and I an able to measure
> > >the temp with fair accuracy.
> > >
> > > Now my concern is this; how much heat can the circuit
> > >board stand before it turns to junk? My plan is to heat
> > >the circuit board with the smt parts and solder paste
> > >and finish this off with the embossing tool that Cash
> > >Olsen uses. But, I am worried about the heat on the
> > >board being too much, prehaps some of you have gone
> > >throuh this and know if the boards can stand the heat.
> > >
> > > Bruce K3CMZ
> > >
> > >_______________________________________________
> > >HPSDR Discussion List
> > >To post msg: hpsdr at hpsdr.org
> > >Subscription help: http://lists.hpsdr.org/listinfo.cgi/hpsdr-hpsdr.org
> > >HPSDR web page: http://hpsdr.org
> > >Archives: http://lists.hpsdr.org/pipermail/hpsdr-hpsdr.org/
> >
> > _______________________________________________
> > HPSDR Discussion List
> > To post msg: hpsdr at hpsdr.org
> > Subscription help: http://lists.hpsdr.org/listinfo.cgi/hpsdr-hpsdr.org
> > HPSDR web page: http://hpsdr.org
> > Archives: http://lists.hpsdr.org/pipermail/hpsdr-hpsdr.org/
>
> _______________________________________________
> HPSDR Discussion List
> To post msg: hpsdr at hpsdr.org
> Subscription help: http://lists.hpsdr.org/listinfo.cgi/hpsdr-hpsdr.org
> HPSDR web page: http://hpsdr.org
> Archives: http://lists.hpsdr.org/pipermail/hpsdr-hpsdr.org/

-- 

Cecil
KD5NWA
www.qrpradio.com www.hpsdr.com


"Sacred Cows make the best Hamburger!"	Don Seglio Batuna

 1154997401.0