Prototyping

Prototyping

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dipchip

Joined: 07 May 2001
Posts: 55

02 Oct 2002 22:28 Prototyping

Like most here I am also interested in electronics apart from my job. I often want to prototype an interesting circuits in a more permanent form than the protoboard strips that I used for testing. I have had mixed result with PCBs, the press and peel stuff works but not that well. (If I gould get this to work better then the "single sided board with jumpers" might be the solution--I know that there are several people interested in this.) I have tried predefined stripboard / vector board but moving the design from the pcb or schematic to the other medium is a pain. Be nice if there was some way to import standard designs into one of these prototyping system.

Anyone have any tips or guidelines to help in the prototyping of these one-of-a-kind projects that they could share?

flatulent

Joined: 19 Jul 2002
Posts: 4849
Helped: 289
Location: Middle Earth

02 Oct 2002 23:06 first class method

If you are willing to spend some money for quality boards, http://www.expresspcb.com/ is a company which will do economical (by commercial standards) two layer boards by email. You use their layout software.

kartofel

Joined: 11 Jan 2002
Posts: 2

02 Oct 2002 23:46 pcb prototyping

AP Circuits in Canada in even more affordable.
On the other hand I also do make my own pcb's. Here is how.
1. get a gerper plot printed on the laser printer on paper or plastic film.
Chose plastic film so that it does not melt. Different printers/toners and different papers proiduce different results. I used transparencies for laser/inkjet.
2. I you use double sided pcb, you will have to print both sides, then cut them out and place in such a way that both top and bottom mach. Then place small strip og blank pcb on one side as a spacer. Insert your blank pcb ( cleaned with abrasive cleaner ) between films.
3. If you make single sided pcb, just place your printout on the the board.
4. Make sure that printed side of the film faces copper!
5. Run everything through the laminator.
6. After board cools off, try peeling the film off the board.
7. Inspect pattern on copper for missing fragments of traces or pads and touch-up with a sharp permanent marker or pcb marking pen.
8. Etch and drill.
Works for me. It does produce shabby looking boards but for protos or proof of concept is ok.
Bregs Very Happy

CADDevil

Joined: 26 Jun 2001
Posts: 122

02 Oct 2002 23:54

I am doing it this way:

1. Design the circuit, draw schematics and design PCB board.
2. Print PCB design to transparent foil in laser printer
3. Put the foil on the photosensitive PCB material
4. Put under UV lamp for 5 minutes
5. Develop and etch
6. Clean the bathroom (very important, especially if you are married)
6. Drill holes
7. Solder parts

CADDevil

Joined: 26 Jun 2001
Posts: 122

02 Oct 2002 23:58

But I think that the days of prototyping at home will soon be over.
More and more parts are only in SMD packages. It is possible to do PCBs with tracks and pads for SOIC and similar chips at home, but for SSOP, TQFP and other packages with 0.65 mm distance between contacts, it is impossible.
Also, high speed design is pain in the a** on only two layers.

I only hope that the PCB houses will lower their prices, if more and more hobbyists will start to order professionally made boards in prototype quantites.

Designer01

Joined: 27 Sep 2002
Posts: 11

03 Oct 2002 0:49

Try www.eurocircuits.com

With online price calculator

greetz

mrmookiebud

Joined: 04 Oct 2002
Posts: 19

05 Oct 2002 12:13

This is probably out of the league of the average hobby electro but one method I've used is to mill out circuits. Now, I happen to have built a mill to do that but I think there are some out there for the sort of $1200 USD range. It really comes down to a cost trade off. Over the years of spending alot of money on prototypes from people like AP circuits, I thought I'd invest myself. AP Circuits however does offer a pretty good service (and fairly nice boards).

kot_b

Joined: 28 Dec 2001
Posts: 111
Helped: 3
Location: Latvia

22 Dec 2002 14:43

Guy's, but what do you think about producing PCB at home? I know, there are one men in Latvia, wich fully realize PCB producing process at home, expect only solrer resist layers...

Pim

Joined: 26 Jan 2002
Posts: 78

22 Dec 2002 18:32

I've too have made a lot of home-made circuit boards. With some feeling for details and a lot of patience it is possible to make quite good boards.

The biggest cost and problem at the moment is where to find a cheap shop to photo-plot the films. With good photo-plotted films at hand the result is likely to be rather good.

Does anyone have a tip of where (preferably in Europe) one could send layout data by e-mail and get a photo-plotted film in the mail in return for a cheap cost and conviniently fast?

Pim

kot_b

Joined: 28 Dec 2001
Posts: 111
Helped: 3
Location: Latvia

22 Dec 2002 18:36

Hi, Pim
But what do u think about using LaseJet and transparent film for photo-plotting?
And how u create a plated drills

Nick C.

Joined: 20 Dec 2002
Posts: 184
Helped: 4

22 Dec 2002 21:44

One hint if using transparencies - print your art
mirrored. That way you can flip over the transparency
and the art/toner will be in direct contact with the
photoresist on the PCB. This keeps light from leaking
under the edges, and makes for cleaner/crisp tracks.

Nick C.

kot_b

Joined: 28 Dec 2001
Posts: 111
Helped: 3
Location: Latvia

23 Dec 2002 1:06

Yep about using it's OK, but what about plating? It seems that it can be done with Ag(NO2) or some thing like that?

junglejenny

Joined: 25 Nov 2001
Posts: 76

23 Dec 2002 5:25

I've had my fair share of home pcb development and I have enough holes in my clothes and carpets to prove it.
You can't beat a proffesional but you need to do some level of testing whilst an idea is burning in your head.

The problem as well as plated through holes ( or the lack of them ) is getting a good image as I find. Photo plotting would fix the problem but you can't find many photo plotting services open at 3AM.

Latest Idea Shocked

:
Epson has just released a new printer that can print on flat surfaces upto 1.3 mm thick. This inkjet printer also can be used with indellible inks. If the ink is acid resistant then Epson is going to make a lot of money out of people like us. Epson is promoting this feature for printing directly on CDs.
This is also an A3 printer.

http://www.epson.co.uk/product/printers/photo/styphoto2100/index.htm
http://www.epson.co.uk/product/printers/photo/styphoto2100/spec.htm

Please if any one has access to one of these, try it out and let the rest of us know.

Seasons greetings.

JJ

DrShoe

Joined: 16 Apr 2001
Posts: 35
Location: Netherlands

09 Feb 2003 22:24 Epson Stylus Photo 2100

Good idea, did you made any progress?
The epson is a quit expensive one €760,-

The board I have is 1.7mm thick.
And water resistant may be a problem, but if it works its worth the money.

Right now I'm plotting on a HP7475 with a steadtler 313 but it takes a lot of time and driving from windows is not possible (yet) results a perfect.

esprx

Joined: 15 Feb 2002
Posts: 14

12 Mar 2003 23:52

I've read about some positive experiments using an Epson inkjet with shellac-based ink. The etchant-resistant ink has to be mixed/made by the experimenter him/herself, and after printing with the shellac ink cartridge you'll have to clean the print head with solvent (isopropyl alcohol or ethanol) in order to prevent clogging of the piezo jets. In theory this works well.

There's a Yahoo group called "Selfmade PCBs", and this idea came from there. Plenty of other ideas as well.

Cheers,
esprx

hobbymat

Joined: 16 Feb 2003
Posts: 35

13 Mar 2003 0:12

A decent film can be have made at any modern print shop with a photoplotter. They might make an A2 or A1 size film (with many PCB projects) for a reasonable price for a hobbyist. You'll probably need a postscript file.

A selfmade film can be printed with a decent laser printer that has a good toner cartridge/drum. Some people like to print on transparencies, but in my opinion a much better printout can be made on translucent drawing film. Black is really black, and you won't have to put two films on top of each other like with transparencies.

The PCB milling method is nice, but it costs like hell even if you have a selfmade CNC machine to do the work, due to the tooling costs. The narrow mills that are used in commercial PCB mills cost something like 20 euros/dollars a piece, and you can't mill very many glass-epoxy (FR-4) boards with one tool before it gets just enough dull to produce horrible quality. I've used these PCB milling machines for five years now, and I'm now planning something different and more cost-efficient.

So, a better approach would be a selfmade CNC mill that moves a sharp, focused UV light point on a photoresist-coated PCB just like a milling tool. After developing and etching the board, the machine can be used to drill and cut the board with a Dremel. Almost like an LPKF machine, but less costly to use, and with less fiberglass dust in your respiratory system.

I'll have to put up a web page when I get the machine up and working... Smile

Hobbie

dipchip

Joined: 07 May 2001
Posts: 55

14 Mar 2003 17:14

There have been a lot of good ideas discussed. i would love to hear more about the inovative approaches mentioned.

Has anyone considered reversing the process. Add copper to the board instead of remove it.

Possibly an adhesive application with the desired pattern, a dusting with powdered copper, thermal cure, and a tinning operation? This should have considerable economic savings as well as reducing the environmental impact of the processes involved.

badbiki

Joined: 29 Apr 2002
Posts: 24

15 Mar 2003 6:40

what about starting a protoype peer group setup? where everyone submits deisgns at the end of the month in one format, these are all put together into large sheets to be made. so 10 or so designs per board.. 10 people over $200 brings the cost of prototyping down to sfa Smile

so buy in quantity, but group everyone into this scheme.. it'd even be possible to write some scripts to sort pcb's and workout the best options... submit a new designs, say how many proto boards wanted.. cost is worked out by how many designs are submit'd, total area etc Smile

would this not be a fesable option?

Also, how hard would it be to setup a plotter with a UV light? and use this to mark the boards? one soleniod for controling a shutter and then normal x-y movement... no?

esprx

Joined: 15 Feb 2002
Posts: 14

15 Mar 2003 14:44

You can make an inexpensive UV source by buying a LED money detector that has a UV LED. Combine that with a focusing lens taken from an old CD drive and you'll have a very intense, small UV dot. A bit sharper and more defined dot can be achieved by adding a small aperture (like 0.2 mm) in front of the lens, close to the board surface.

All this can be made to fit the pen holder of a plotter. After that it's just a question of the right pen speed and availability of the plotter drivers.

It might be a good idea to feed the LED with some other source than the default button batteries that can go flat quite easily. The maximum current might be in the 15 mA range, in order not to kill the LED prematurely - the UV LEDs have typically a much shorter life span than those of longer wavelengths.

I'm going to use this approach with a homebuilt flatbed cnc mill, not a plotter, so that I can drill and depanelize the board with ease... Smile

Cheers,
esprx

badbiki

Joined: 29 Apr 2002
Posts: 24

15 Mar 2003 16:58

yes that'd definatley be the way to do things! may be about time to buy an old plotter and modify it...

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