Question about PCB software (and making the boards at home)

Gunnar wrote:
> Now with surface mount ICs it is scary trying to
> make boards...

I don't think boards are a problem - someone else mentioned
expresspcb.com, so that covers you for boards.

The trick with SMD is assembly.  Thru-hole is easy, but DIP parts are
huge.  To really make the most of the $51 boards from expresspcb (and
to use modern components) you can't help but use SMD.

But with SMD you need at least these two things over and above what you
normally stock in your lab:

+ A large magnifier (or microscope depending on your vision).
+ A toaster oven.


I like to hear people's experience with toaster ovens for SMD soldering
of QFPs and other ICs.  There are various bits on the web about it, but
it's always good to hear the latest techniques.

Paul Marciano wrote:

> But with SMD you need at least these two things over and above what you
> normally stock in your lab:
> 
> + A large magnifier (or microscope depending on your vision).
> + A toaster oven.
> 
> 
> I like to hear people's experience with toaster ovens for SMD soldering
> of QFPs and other ICs.

I do quite a lot of S&M prototyping, and I've never used either a large 
magnifier nor a toaster oven (British toasters of the pop-up type are 
deprecated anyway). I've not tried BGAs, nor QFPs above 200-odd pins, 
but simple hand assembly works well up to that point. The Pace Wavetip 
is useful, but an ordinary soldering iron (coarse tip- say 1.5mm) works 
almost as well. As follows: Flux all over the pads and position the IC. 
Use the fine tipped iron to tack the corner pins on (doesn't matter if 
you blob a bit). Melt a bit of solder on the wavetip or coarse bit, then 
draw it upside down along all the pins. Finally, clean up pins with 
solder wick.

For resistors, SOTs etc. just tweezwers and solder by hand. It's quicker 
than through hole.

As for the magnifier, I use a jewellers loop to inspect, but I'm 
shortsighted enough that the whole thing is in focus 6" in front of my 
nose, and with a good light, that works OK.

Paul Burke

Paul Burke wrote:
> 
... snip ...
> 
> I do quite a lot of S&M prototyping, and I've never used either a
> large magnifier nor a toaster oven (British toasters of the pop-up
> type are deprecated anyway). I've not tried BGAs, nor QFPs above
> 200-odd pins, but simple hand assembly works well up to that point.
> The Pace Wavetip is useful, but an ordinary soldering iron (coarse
> tip- say 1.5mm) works almost as well. As follows: Flux all over
> the pads and position the IC. Use the fine tipped iron to tack the
> corner pins on (doesn't matter if you blob a bit). Melt a bit of
> solder on the wavetip or coarse bit, then draw it upside down
> along all the pins. Finally, clean up pins with solder wick.

Just for contrast, I was taught to always have a solid mechanical
joint before soldering.  We spent much time twisting leads with
long nosed pliers.  Only the very sloppy used the solder as glue. 
Hi-tech was a single sided PC board.

-- 
"If you want to post a followup via groups.google.com, don't use
 the broken "Reply" link at the bottom of the article.  Click on 
 "show options" at the top of the article, then click on the 
 "Reply" at the bottom of the article headers." - Keith Thompson

Paul Burke wrote:
> I do quite a lot of S&M prototyping, and I've never used
> either a large magnifier nor a toaster oven (British
> toasters of the pop-up type are deprecated anyway).

Yeah, that's a good tip - don't use a pop-up toaster for SMD soldering.
I knew a guy once who tried that...  didn't work... and the toast never
quite tasted right after that.

Really?

No, not really.

If you google toaster oven SMD you'll get some hits with photos of the
process.  I must admit I haven't tried it myself, but it looks
fascinating.  I gather there's a knack to it and it takes a few tries -
so it's best to have some sacrificial components.

One pin at a time is old-school (if there is such a thing when
discussing SMD), but if you have good eyes and a steady hand it's
doable, although you must take care not to overheat the leads.

A toaster oven, with the right thermal profile, can apparently do a
very good job and handle an entire board's worth of SMD parts in very
short time (although you still need to carefully inspect and fix
bridges, etc).

If I were doing a lot of SMD boards, I would at least give it a go.

Paul.

Paul Marciano wrote:

> A toaster oven, with the right thermal profile, can apparently do a
> very good job and handle an entire board's worth of SMD parts in very
> short time (although you still need to carefully inspect and fix
> bridges, etc).

Presumably you have to screen the solder on first? Or paint it on with a 
brush? Then place the components with a steady hand, making sure they 
don't move between placing and heating.

No, I'll stick to my state-of-the-ark hand method for now.

Paul Burke

On 25-Apr-2005, "Paul Marciano" <pm940@yahoo.com> wrote:

> But with SMD you need at least these two things over and above what you
> normally stock in your lab:
>
> + A large magnifier (or microscope depending on your vision).
> + A toaster oven.
>
>
> I like to hear people's experience with toaster ovens for SMD soldering
> of QFPs and other ICs.

I've got a large magnifier and toaster oven, and they work quite well. I
will lay-out several different proto boards
on a panel, get a prototype stencil make for the panel, and go from there.
Once the panel has been assembled
and soldered, I cut the boards apart with a diamond blade on a table saw.
The prototype stencil costs $150 US.

I'ts not worth the trouble for a little board with a couple of dozen parts,
but you can save a ton of time as the parts
count goes up.

I've been doing 0.5MM pitch QFPs without too much trouble.

There is some useful information at http://www.stencilsunlimited.com/. I've
been buying my stencils here, and
the service is good.

As far as the magnifier, I bought a Vision Engineering "Mantis" off of ebay
a couple of years ago. Once you've had
one of these babies in your lab, you will find that you can't get by without
one. A 6X lens works well for me.

-Hershel Roberson

Paul Burke wrote:
> Paul Marciano wrote:
>
> > A toaster oven, with the right thermal profile, can apparently do a
> > very good job and handle an entire board's worth of SMD parts in
very
> > short time (although you still need to carefully inspect and fix
> > bridges, etc).
>
> Presumably you have to screen the solder on first? Or paint it on
with a
> brush? Then place the components with a steady hand, making sure they

> don't move between placing and heating.
>
> No, I'll stick to my state-of-the-ark hand method for now.
>
> Paul Burke

Here's the reference:
http://www.seattlerobotics.org/encoder/200006/oven_art.htm

As I said, I've never tried it myself, but it does look interesting.

Never hurts to try new things (except skydiving without a parachute).

> I like to hear people's experience with toaster ovens for SMD
soldering
> of QFPs and other ICs.  There are various bits on the web about it,
but
> it's always good to hear the latest techniques.

It's superficially very easy, but the devil is in the details,
particularly if you are trying to achieve a zero rework rate. For
fine-pitch QFP, simply squeezing solder paste onto the pads,
hand-placing parts and dropping the PCB into a toaster oven gives what
I'd call "80/20 Pyrrhic results" - i.e. most of the time, 80% of the
joints are good, but fixing the remaining 20% takes as much time or
more as it would have to hand-solder the entire thing.

I'm working on a project (which I'll probably market as a kit) that
combines a non-contact temperature sensor with a simple PWM controller;
you hack it into a toaster oven to turn it into a reasonably controlled
reflow oven. It can handle the full preheat - reflow - cool temperature
profile.

There are a lot of engineering difficulties with this approach, though.
In the preheat phase, I've discovered you really want positive air
circulation. You absolutely don't want it during the reflow phase,
though, because components "sail" across the solder surface in those
air currents.

What is a toaster oven ?

Is it a thing for doing toast whilst keeping said toast
horizontal ? Is it like an ordinary oven grill with
heating elements top/bottom ?

Or is it a combined oven and toaster ?

Richard [in PE12]

Jet Morgan wrote:
> What is a toaster oven ?

Talkie's the name, toasting's the game. Anyone want any toast?

It's a small front-loading electric oven, typically about 45cm wide by
25cm tall by 25cm deep (interior cavity) with heating elements at top
and bottom. Cheap ones are under US$20 at department stores. Typically
used for heating a grilled cheese sandwich or a mini pizza or similar
fodder.