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

Hey!

I've not used PCB123 but have used ExpressPCB

with success and satisfaction.

I agree, and it's so much easier to let them deal with the ugly details of board production. Just not having to deal with spent echant disposal makes it worth the price!

Yer welcome.

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          Michael Kesti            |  "And like, one and one don't make
                                   |   two, one and one make one."
          mkesti@gv.net            |          - The Who, Bargain

I meant to add this link to an 8051-based MIDI Timecode display I did using ExpressPCB's software and services.

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          Michael Kesti            |  "And like, one and one don't make
                                   |   two, one and one make one."
          mkesti@gv.net            |          - The Who, Bargain

I agree that getting a professional board fabrication outfit to build the board is often better than doing it yourself. Unless you have plenty of time and the right equipment at home you will find that the cost of doing the board building can often be met by some more overtime at your normal day job.

As for decent CAD tools then I suggest looking at:-

They apparently do a Linux version as well as a Windows version. There is a free download that you can use for small projects. If you need a bigger board capability then you can buy the extra capacity.

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Gunnar

I can't comment on the free PCB software you mentioned, but some words about home PCB production:

- SMD does not complicate things. In fact it's making things often easier.

- Making your own boards is having a lot of advantages, but the degree of the advantage may vary greatöy on where you are located etc. I.e. where I live, "in country" made PCB's are horribly expensive and haveing them made at cheaper locations add's a lot of aditional delay.

- You can do quite cool PCB's at home if you are dedicated. I.e. I'm making my own though plated multi layer PCB's at home. See

If you need ~50 PCBs/year, you will end up with ~$10/board asuming we talk about four layers, 200 holes and 4x4" size. To me, the biggest advantage is not necesarily cost saving. It's the fact that you have the PCB in your hands just some hours after you decided that you need one.

Just my 2¢ of course

Markus

PS: The home made ones are for prototyping and personal use only. Production runs are always made in a boardhouse.

If you have enough space to set up equipment permanently, and can live without through-plating, homebrew PCBs can be fast and easy. For lots of info on making good quality PCBs, see

Hi Mike,

good info! Thanks,

Gunnar,

Markus,

pretty cool!

It seems overkill for me though at the moment. Will keep a link to your site though, one never knows when this might come in handy...

Gunnar

[snip]

Thanks Paul.

Gunnar.

Thanks for the links Michael.

Gunnar.

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.

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

... snip ...

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.

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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.

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

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

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

very

with a

Here's the reference:

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).

soldering

but

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]

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.