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

Started by Gunnar April 23, 2005
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.