You can design, print and etch your own PCBs from a flexible sheet of Kapton coated with a thin layer of copper. To do this yourself you need some special materials and equipment, and if you are not planning on etching circuits more regularly then it can be nice to start by looking for a local space that has an etching setup you can use.

Photo of a flex circuit etched using the exact same process as described bellow in step-by-step detail.

Etching at Machwerk

The following flex circuit was etched at Machwerk in Wedding/Berlin.

Laser-print your design (don’t for get to mirror it!) onto glossy paper. Catalog paper works really well. Wipe the copper surface of your flex circuit material clean with some acetone. It is important that all surfaces stay clean from grease and dirt. Even the sheets of catalog paper you are printing on.

Use an iron or in this case a modified laminator to transfer the toner from your inkjet print to your circuitboard. Run it through the laminator a few times to insure the transfer is good, and you can add a piece of PCB or other thicker material into the laminator at the same time to increase pressure for transfer.

Check to make sure the ink from your print has transferred, this will probably result in the paper sticking to the copper of your circuit. Bathe in bath of soapy water until paper is drenched and will peel off or rub away easily. Remove all paper.

Dry and mount on a non-flex material (piece of PCB or plexi) to stabilize for etching bath. Devise a way of mounting using either double-sided tape or all-plastic clips/clamps. Spray mount didn’t work too well, and came undone in the bath.

The etching bath is heated to 40-50°C and bubbles rising from the bottom ensure that the liquid stays in motion and the copper surface will etch evenly. The copper surface to be etched should be evenly exposed to rising bubbles, so it is important to mount the flexible material on a substrate that will keep it in place throughout the process.
This particular etching bath is constructed to minimize amount of enchant required. Heating comes from a halogen light bulb inside a test-tube filled with sand. Cooking thermometer is used to keep track of temperature. Aquarium pump pumps air into a perforated tube lying at the bottom of the bath.

Depending on the quality of the bath, etching should take 3-10 minutes. The following video shows the final stages of etching where you can clearly see the copper disappearing and the circuit emerging.

Video:

Remove etched circuit from bath and rinse etching liquid off circuit and mounting apparatus in sink with tap water. Use acetone to rub off toner transfer.

Looking at circuit under microscope you can see how the copper traces are clearly separated, but also how the copper has been affected by the etching process.

Drill or poke holes through material for through-holes or vias.

Close-ups: left) drilled hole, right) poked hole

Etching in Studio

The following circuit was etched using xxx and xxx in our studio. The transfer was made by going to local print shop to laserprint circuit onto regular paper or transparency foil and transferring by iron. The transfer process was not ideal so the circuit either etched too much or too little of the copper. Though with more experience this setup can definitely also be made to work.

Lasercutting Soldermask at Fablab Berlin

At the Fablab Berlin we lasercut the soldermask from a sheet of kapton that has a layer of heat-fused adhesive on one side. The soldermask is supposed to cover all of the copper traces that don’t need to be exposed for soldering or contact points.

Download Visicut:
>> http://www.fablab-berlin.org/de/downloads/
Download and import settings:
>> http://www.fablab-berlin.org/de/downloads/
Lasercutting settings that i used: speed 100, power 10, frequency: 5000

Create file in Illustrator and use different colour lines to control what gets cut first. You want to cut out the small inside shapes before cutting the outline. Export SVG.

Import SVG to Visicad:

Lasercutting:

Lasercut-soldermask:

Fuse soldermask to etched circuit using modified laminator or iron on high heat:

Materials:

Pyralux® Flexible Laminates by DuPont:
>> http://www2.dupont.com/Pyralux/en_US/products/laminate/
Ebay >> http://www.ebay.com/sch/i.html?_trksid=p2047675.m570.l1313.TR0.TRC0&_nkw=Pyralux&_sacat=0&_from=R40

Links:

Nice Instructable on DIY Flexible Printed Circuits:
>> http://www.instructables.com/id/DIY-Flexible-Printed-Circuits/

Syuzi Pakhchyan has a very nice tutorial for DIY circuit printing on diynetwork:
>> http://www.diynetwork.com/diy/cda/article_print/0,1983,DIY_13721_5708736_ARTICLE-DETAIL-PRINT,00.html

One of the problems with etching PCBs is that the etching chemical ends up as toxic waste. Here is a nice Instructable for an alternative etching chemical:
>> http://www.instructables.com/id/Stop-using-Ferric-Chloride-etchant!–A-better-etc/