Flexible PCB : DIY Method For Pro Grade Circuits

Adding Flexible PCB to Fabricated PCB Will Give Professional Result. We tested many methods – from ething various copper tapes, thin copper sheets to DuPont’s Pyralux flexible circuit material. We will suggest to go with DuPont’s Pyralux flexible circuit material or similar product. Here is Detailed Guide on Flexible PCB – DIY Method For Pro Grade Circuits. Of course, we have to follow designing norms of SMD components, not through-hole components. However, we can add male or female headers at ends. Specially for connecting display units, flexible PCB really great. Of course, in certain projects flexible PCB alone is sufficient. Flexible PCB has own designing standard. We need not to strictly follow that for ordinary DIY works. You can read about flexible circuit in this PDF :

 

Flexible PCB : DIY Method Tools and Materials

 

DuPont’s Pyralux flexible circuit material available in all countries we commonly now. Pyralux AC 352500EY 6″x 6″ sheet costs around 9 USD per sheet – yes, it is costly. Cheaper alternatives not exactly great, although you can test :

1. Conductive copper tapes with conductive adhesive : It is worst idea to use. It is for using as if there is no resistance of adhesive. You simply end-up with short circuit. It is good to make small circuit on PVC visiting cards or wiring prototyping boards. It is a good thing to have in box.
2. Conductive copper tapes with non-conductive adhesive : Although appealing and may work, it actually messy. One big problem is thickness of copper (0.1mm is our minimum need). You can not really get the needed strength of the material to use it alone. It is basically for guitar like instruments.
3. Thin copper sheets for artworks, religious writing : Specially copper sheets for religious writing are enough good from many points. They are cheap & has nice thickness. They are good for hand drawing small circuit and laminating the whole stuff, then making holes to use. Otherwise, how you’ll stick the circuit’s one side? It is messy than it sounds. It is excellent tool if properly used.

DuPont’s Pyralux flexible circuit material uses Kapton polyimide film. You commonly see yellow or amber colored transparent connecting ribbons in circuits. Kapton itself developed by DuPont in 60s and patent is of various companies. The material can tolerate +400 °C. Only Kapton tapes also available – you can stick over the circuit (if it is like connector) to avoid chance of short circuit. NASA uses the material for various purposes.

So you need :

1. DuPont’s Pyralux flexible circuit material or similar material
2. Isopropyl alcohol to clean the protective layer of copper side of Pyralux
3. Fine grit sandpaper to rub copper side of Pyralux
4. Soap & scrubber used in kitchen to rub copper side of Pyralux
5. Laser printer. We use Samsung’s ordinary B&W laser printer.
6. Some glosy paper which will print the circuit and transfer to Pyralux
7. Better to have a laminator machine, otherwise use household iron to heat transfer the laser print to Pyralux
8. Copper Chloride in Aqueous Hydrochloric Acid Solution for Etching

This is official product webpage of Pyralux :

 

Steps to Make Flexible PCB

 

Steps to make/etch flexible PCB exactly like normal PCB. If you are newbie around it, you can carefully read this detailed article for etching NORMAL PCB, practice on NORMAL PCB :

PCB making kits are available from local shops to Ebay, Amazon. NaPS is a risky chemical, usually alternative chemical supplied in kits. Basically these days, building ordinary 1-2 layer PCB is better with online PCB fabrication and assembling services. Giving them $10 when does the job, why waste time? That is fact. But case of Flexible PCB is different at this moment.

As for detailed steps for Pyralux, we are doing same steps. Cut out a piece of Pyralux around half inch larger than the circuit board tracing. Go closer to sink, wear gloves at this point. First spray isopropyl alcohol to the copper side of Pyralux, let dry. Then spray or paint with acetone and let it dry. Then rinse with water. Thereafter rub with fine grit sandpaper, carefully like polishing. You’ll see that copper’s shine becoming obvious. Then use soap & scrubber used in kitchen to rub copper side of Pyralux to make it fully shiny.

Now, refer printing the circuit board tracing on shiny paper or transfer paper in the way written in this site :

Use tapes to secure the design on Pyralux, run inside laminator. Do not cross more than 350 °C. You have to run few times, may be 6 times. Then simply put paper with Pyralux in a bucket full of water so that paper easily comes out. After Pyralux with print gets dry, put it inside copper chloride and hydrochloric acid solution into a plastic or glass pan. Keep it for an hour or so, uncoated part of copper will go away. After you see work is done, take out the Pyralux, rinse with water, submerge in adequate amount of water and check pH with pH paper or litmus paper to make sure no acid preset. Blue litmus becomes red in presence of acid.