PDA

View Full Version : OT sorta electronics, PC boards and stuff that goes zap!!



Forrest Addy
05-25-2008, 11:15 PM
This is OT sorta but related to electronics, PC boards and stuff that goes zap!! There's plenty here who meld electronics with machine tools so I think I'm on a safe OT.

I needed a custom printed circuit board recently but what a hassle to make them. The raw board material, the artwork, the mystery of getting a good exposure, the developing and etching with nasty chemicals, and finally the drilling with dinky little drills. Expensive and a PITA but them days are gone. I discovered:

http://www.expresspcb.com/ExpressPCBHtm/Specs.htm

A printed curcuit outfit that's a one stop shop. They have a number of entry and prototype plans and they GIVE you the printed curcuit artwork for boards up to four layers.

The costs are not cheap but they are affordable for someone working on a small scale. The price beats the start up price for a few PC board by a mile. I paid $57 incl shipping for four drilled and plated boards measuring 2.5" x 3.8". I crammed four smaller boards onto the area and got 12 at about $5 ea.

Also included is circuit diagram software complete with a library of digital devices. Naturally everything is live linked. You drag the chip and the connections stretch to follow. The circuit board software is intuitive and has many features. I mastered it well enough in a few hours of fiddling to design my board and send it off via a live link to the ExpressPC. They will be shipped the next day if the design is in by deadline and you will receive them in three business days.

No connection (no pun intended either). Just a good service I discovered and wish to share with the other wire rubbers.

There are other prototype PC board services out there but this one seemed to be almost painless.

Yes, I multi posted this.

Fasttrack
05-25-2008, 11:20 PM
There used to be one of those in our university town but they closed recently. Now everything for our labs is done via breadboard unless its important enough to warrant the trouble of producing our own board.

Dawai
05-25-2008, 11:28 PM
I used them and their software while working on my own stepper drives..

Kinda wild ain't it? about a few years back that software would have cost a half million dollars. THEN the SPICE software started, I think this is a offshoot.

I used to do my circuit boards in Autocad, then flip them make a printout, then take it to a print shop to make a photo positive, then expose my own boards,and wash them, then drill them, then solder them.. then laugh like a madman when a radioshack purchased second rate device smoked the whole project.

The world is limited by only your imagination, and your inept ability to learn new things.

fasto
05-25-2008, 11:35 PM
I use a house called Advanced Circuits for almost all of my PCB's. They're fabbing 3 boards, 50 pieces each, for me right now. I use PCAD for layout, but they offer their own layout tool as well. www.advancedcircuits.com
They have a bunch of specials, like 5 pcb's, 60 in^2 max each, 2 layer, 5 day turn, $120.

I use a house called Screaming Circuits for my small PCB assembly jobs. They're running a 15-board order for me right now. www.screamingcircuits.com

I used Express PCB a couple years ago but I like the pcb's from Advanced Circuits better.

nheng
05-25-2008, 11:48 PM
We use a number of houses and have also used Advanced Circuits. Screaming circuits assembled some larger boards for us a while back and did ok. For smaller, quick turn boards I think we are currently using PCBExpress which I think was the PCB partner of Screaming circuits but I could be mistaken.

We use Mentor/Pads for schematic capture and PCB layout.

Surface mount stuff is actually pretty easy to assemble. If you are doing any high lead count and/or finer pitch parts, it is worth the money, even on a few up, to get a proper solder mask.

If someone is doing your assembly for you, be sure that your parts are accurately "kitted" up with reference designators, etc. It's not fun to watch the magic smoke leave tiny SMT parts, some with volcanic like action (small flame, smoke plume). Den

C - ROSS
05-25-2008, 11:49 PM
Good grief

When I was doing prototype boards I had to start from scratch, do the art work by hand no such thing as auto cad, then the photo work and then wash and drill. Now it is so easy a kid can do it.

Forest thanks for the info. I don't expect to do any more of that type work again but if the need comes up I now have access to the easy way.

Ross

Swarf&Sparks
05-26-2008, 12:18 AM
For a quick and dirty prototype (through-hole only) I used to take a CAD drawing, DXF, to my local vinyl sign shop. Get em to cut a mask on the plotter. Stick it to the copper and etch in hot ammonium persulphate. Only prob was tiny bubbles at the edge of the mask. Easily cured by brushing with a plastic paintbush (kids paintbox type) during etch.

Weston Bye
05-26-2008, 06:11 AM
I started out the same way that David described, until my photographer went out of business and I couldn't get my artwork photographed and high contrast litho negatives made.

Since then I began using Advanced Circuits for small to moderate quantity prototypes at work. Saved gobs of money and time for the company over their usual method of dealing with their usual sources.

These instant board companies don't get their work done in China, do they?

AlleyCat
05-26-2008, 09:51 AM
I make my own boards since I have a photoplotter, laminator and the etching equipment. If this equipment wasn't in my shop I would use one of the companies mentioned. It's hard to believe they can do it for so little. I don't think they are getting these boards from China but there are companies in China offering similar services.

fasto
05-26-2008, 09:54 AM
All of the companies that I have mentioned do their work in the US. Most do offer a Chinese arm for higher volume or longer lead times.

There are Chinese quick-turn PCB and Assembly outfits, some have a good reputation, but I haven't used any of them, and I prefer not to.
--
Aaron

lwalker
05-26-2008, 04:31 PM
These instant board companies don't get their work done in China, do they?

Some do. Eastern Europe is another popular source. The one I use has a Texas address, but when the boards arrived 10 days later, I was surprised to see that it was in a Chinese candy box (!) with a DHL shipping label that listed country of origin as China.
Excellent quality boards: my first order was 5 pieces of a 2x3" board double sided, with PTH and mask both sides. Cost was $80 including shipping!

I have since ordered a few more prototype runs from them and one order of 100 pcs of the same board for about $2.50 each. Again, that included shipping. I don't care about country of origin as long as the quality is there: outsourcing works for the "big guys", I don't see why it shouldn't make money for me too.

There is a service called batch PCB run from the Sparkfun.com site. It is very cheap: basically they take orders from a bunch of people and batch them together into one order to get economy of scale, then separate them at the end. I haven't used them but I hear the quality is good and the price is very low, but you may have to wait 3-4 weeks to get a board back.

KiloBravo
05-26-2008, 04:43 PM
For design layouts I like to use Eagle they have a free version for non commercial work >>> http://www.cadsoftusa.com/

These guys use to be the cheapest for getting a board made
http://www.olimex.com/pcb/index.html
Only problem is it takes 10 days to ship to the USA. I think they are in Bulgaria.

snowman
05-26-2008, 09:34 PM
sparkfun electronics also has a pcb option, you don't have to fill a full plate either.

it is chinese manufacture though

Paul Alciatore
05-26-2008, 11:55 PM
I have also used expresspcb, but I am presently trying out Advanced Circuits

https://www.barebonespcb.com/!BB1.asp

They seem to have better service for about the same price and their free software is worlds more capable than the program expresspcb provides. I am doing a small board that will fit two each on the 2.5" x 3.8" size that both companies will make for a very reasonable price. I'm going through the learning process with the software now.

I also have made PCBs myself and the process is definitely doable at home or in a small shop. You must make an exact, full size positive or negative of the circuit and that is contact printed onto the sensitized copper clad board. A simple solvent style developer is used to disolve away the mask where the copper is to be removed and then it is placed in an etchant bath for 10 - 30 minutes. Steel wool can be used to remove the mask and the copper is ready for soldering. You can even purchase a tin plating solution that takes just a couple of minutes to plate the copper. But, yes you do have to drill all those holes and that can be a real PITA. Much easier to get them done. And probably just as cheap.

darryl
05-27-2008, 04:24 AM
Hmm. My latest circuit boards don't even have copper on them, just holes. With only about a dozen parts, I'm just pushing the leads through then bending them over in the direction they need to go. There was only one place where the part leads weren't long enough to form the 'trace', and a piece of solid telephone wire took care of that.

I most often draw out the circuit pathways with a permanent marker, then etch. Sometimes I drill first, sometimes not. I don't mind doing multiples this way if the circuit is very simple, but for more complex circuits, it drives me crazy just to draw one pattern. I once drew a 6x8 circuit board this way, and with dozens of ic's it was taxing to make sure I got it right before etching. If I'm doing multiples of simple boards, I'll drill first, then just 'connect the dots' with the permanent marker to define the pattern of traces.

Who needs a board house when you can use up hour upon hour of your own valuable time doing it yourself at home :)

Here's some useless info- I have in my attic six etching tanks, each about 14 inches long, an inch and a half wide at the bottom and four inches wide at the top. The etchant is circulated by a small propellor on a fiberglass shaft, which runs in glass bearings. VCR loading motors run these props, which turn inside an external tube connected to the tank top and bottom. The ill-fated project died before I could put them to use.

Weston Bye
05-27-2008, 05:59 AM
Hmm. My latest circuit boards don't even have copper on them, just holes. With only about a dozen parts, I'm just pushing the leads through then bending them over in the direction they need to go. There was only one place where the part leads weren't long enough to form the 'trace', and a piece of solid telephone wire took care of that..

Indeed. This is the approach I've taken for articles I write for Digital Machinist, where a circuit board may be justified, but a printed circuit may not be. The method works for those who may be more machinist than digital.

Perhaps I may offer a printed circuit in the future if the project seems to have popularity potential.

Paul Alciatore
05-29-2008, 03:20 PM
Hmm. My latest circuit boards don't even have copper on them, just holes. With only about a dozen parts, I'm just pushing the leads through then bending them over in the direction they need to go. ........

I often need to build small circuit boards on a one-off basis. Going to the trouble of making a PCB is not the most economic way to proceed. For these I usually use one of the perf boards with generic foil patterns on them. They can be purchased from Radio Shack, Digi-Key, Newark, and most other electronic suppliers. Many different varieties are available depending on what kind of components you are using. The most popular are the styles which copy the pattern of the common breadboards for DIP ICs (twin rows of three hole foil strips arranged on opposite sides of two power busses). Your layout on these just follows the pattern of the breadboard circuit.

If I need more than one, but only a few copies of a circuit board, then I usually jump to wire wrap. A plain perf board without any foil or just an edge board connector pattern is used. Vector has individual pins that can be inserted wherever components are to be mounted.

http://www.vectorelect.com/Catpdf/New%20Page%2073.pdf

I like the T44 terminals as they are the smallest and can be placed side by side on a 0.1" grid providing a good circuit density. Parts are soldered in the pins above the board and wiring is wrapped below. ICs are mounted in wire wrap sockets that I install with a bit of epoxy (the "modeling clay" type) under them. Then I use the Vector Slit and Wrap tool to do the wiring. I keep a supply of different colors of the wire to allow color coding the various connections.

http://www.vectorelect.com/Catpdf/New%20Page%2078.pdf

Wiring paths for power and ground can be doubled or even trippled up to obtain a lower impedance (higher currents). The Slit and Wrap tool makes this easy as you can "chain" the connections from one pin to the next. This means you can connect multiple pins with one continous wire run and only need to cut the wire after the last pin is wrapped. This saves a lot of time when wire wrapping.

I have made many circuit boards this way and have never had any problems with them. You do need to be careful when doing the wrapping as the wire is small and can break. When wrapping a pin, I never allow the tension in the wire to go slack. I hold tension on the tool with my other hand while changing my grip. This helps keep the bite of the post into the wire constant at each corner of the wrap. Once it is properly wrapped, it lasts as well as a PCB. I just completed two boards for a circuit I needed at work using this technique. It is a circuit to detect out of phase stereo audio signals and sound a loud audible alarm as well as light a red LED if an out of phase condition exists.

Another tool that is useful when doing this is a block of plastic about 3/4" to 1" thick and with a grid of holes on a 0.1" grid. You use it under the board for support and guidance when inserting the pins. You have to make this yourself. I just glued a piece of the plain perf board on the plastic and using the existing holes as a pattern, drilled about 3/4" deep into the plastic. I think I used a 0.040" or 0.050" drill a generous clearance hole for the posts.

I also make a wiring list of all connections before I start wrapping. This helps prevent mistakes.

You can purchase 3/4" standoffs from the same electronic supply houses for mounting the boards. I ususlly get the 4-40 or 6-32 sizes.

If you are only making a few boards, this is much faster and more economical than doing a PCB.

fixerdave
05-29-2008, 04:21 PM
...I most often draw out the circuit pathways with a permanent marker, then etch...

I've read, but never tried, that you can use laser prints instead of drawing with a marker. Just make the print, mirrored I think, and place it print-side down on the board. Iron until the toner melts off the paper and onto the board, and then etch. Supposedly, it works fairly well, though traces tend to get eaten around the edges, and small ones can disappear.

I do, however, use the same trick for marking wood with graphics (http://workshopdave.blogspot.com/2007/09/laser-printing-on-wood.html). Print, iron, and you're done. It's the quickest way to put any drawing on wood. I bet it would work well for sheet metal too, so long as it wasn't so thick that it dissipates the heat too fast.

David...

darryl
05-30-2008, 04:53 AM
I've tried the iron-on method but wasn't happy with it. I did not use the recommended plastic film (TEK 200 was what it was called then) so that's probably why.

I still have some perfboard, but I'm not really happy with that either. I find the holes are too large and the solder builds up too much before the connection properly 'wets'. By the time I'm done I have a semi-permanent hole and trace pattern burnt into my retinas :)

When it comes right down to it, the method of choice comes back to drawing the trace pattern with a fine tip marker. I'll go from schematic to a part layout on .1 inch grid graph paper, then tape the paper to the board so I can prick mark the hole locations. Drilling is next, followed by de-burring then a thorough cleaning and copper prep. I don't touch the copper with my fingers from this point on until the etching and first washing is done. Drawing the traces is just connecting the dots, avoiding shorts, and then re-inking traces that don't look dark enough. Then I use a scraper to remove the ink.

The circuit boards I'm doing at present are simply plastic laminate pieces. If you laminate two layers back to back it doesn't warp and it is strong and also looks nice. Some of the time I save by not having to draw and etch a copper clad board is wasted later in the bending and forming of the component leads to form the circuit connections.

I have tried some of the pcb programs, including express pcb (which I kind of like) but I can't really give a comparison since I've forgotten much of what they're all about. I did run into a lot of glitches, probably because they were demo versions.

These days I'd be more than happy to be able to cnc mill a copper clad board into a trace pattern, but I don't have that capability yet. Going from a schematic to a prepared pc board ready for components without having to pay a lot of attention would sure be nice.