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DIY Flexible Printed Circuits

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Produce your own single-sided flexible printed circuits using a solid ink printer, copper-coated polyimide film, and common circuit board etching chemicals.

You will find flex PCBs inside most cellphones or similar miniaturized gadgets. Flex PCBs are useful for making tiny cables and extremely lightweight circuits.

However, few shops yet make custom flex PCBs for reasonable prices in small volumes.
 
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Step 1: Get copper-coated film

Picture of Get copper-coated film
Get some thin sheets of polyimide which have copper on one or both sides. Polyimide is a yellow polymer with a high melting temperature and is sometimes called Kapton. A common type of copper-coated polyimide is DuPont "Pyralux" material.
Pyralux sheets come in many different varieties of polyimide thickness, copper thickness and adhesive thickness (the "adhesive" is between the copper and polyimide holding everything together.) Copper thickness is given in oz per square foot, while adhesive and Kapton thickness is given in mil (1 mil =0.001 inch).

Pyralux LF7062 (pictured) has 1/2 oz Cu, 1/2 mil adhesive and 1 mil Kapton. This works OK but is a bit thin and crinkly for the printer to handle.
LF9120 has 1 oz Cu, 1 mil adhesive and 2 mil Kapton - seems to work best in the printer
LF9210 has 2 oz Cu, 1 mil adhesive and 1 mil Kapton - stiffer, but works OK

Other options are double sided copper ( a sandwich of Cu/Kapton/Cu held together with adhesive) and a roughened surface, denoted by R at the end of the part number.

The roughened sheets and double sided sheet work OK. However, Pyralux with 2 oz or thicker copper can be difficult to feed to the printer, especially if there is copper on both sides.

See if you can get a free sample from DuPont. Occasionally, Pyralux sheets turn up on eBay.

Cut the Pyralux sheets to 8.5x11 or 8.5x14 inches with scissors or a knife. Avoid smudging the copper with fingerprints or oil, which can block the etch solution later. To protect the printer, try to keep the edges relatively flat and free of burrs.
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rlopez231 month ago

just what i needed , i am building a voice changer circuit to integrate into a Halloween mask, but using a regular circuit board is not good as i would like it to comform to the mask , and with this i can build it to fit in the nooks of the mask, very stealthly

Mark Rehorst3 months ago

Great! This would be really useful in 3D printers where you have to run multiple wires (up to 10 for a single extruder) to the extruder and have the thing free to move back and forth easily. Using wide lines would let you carry the current for the heater and thinner lines could be used for the motor, thermistor, and fan(s).

With the right pattern, you could use this to make custom printbed heaters that are much lighter than the silicone covered nichrome wire things.

bongy4 years ago
Hi *, do anyone know where I can find the pyralux or kapton in Italy or some website tha ships to italy? Cheers, Enrico
astral_mage bongy10 months ago
try alibaba.com have fun!
Katco is a company that is in Europe. They will probably ship to Italy.
antirem bongy4 years ago
I work at a flexible circuit board company and this tutorial is really top notch. 

Id love to see what some of the others have come up with.

illica antirem3 years ago
Hi Tony-
Fancy meeting you in this website.

Joe Mattea
articice3 years ago
Hello, please recommend a simple and available method to fix a torn flexible board, mylar on both sides and thin high precision copper (or graphite) traces inside, serving as a flat cable connecting lcd/camera in a mobile phone, etc.
I also would not recommend attempting to fix this as you could damage some of the components
How will it damage the components?

I think I found a solution - use anisotropic conductive tapes (like those Z-Axis from 3M), but a roll costs ~$300 or so, and I need a few centimetres. I mailed them for samples, but got nothing ;(
My strategy is to use the best pitch possible.
Any ideas where to get a few cm of 3M's 5363 (or 5552R) or 7303?
try alibaba.com u might be able to find it there far cheaper, but u might have wait 4 a few days tho.
The best way to do that is just to source a replacement, fixing those yourself is a pain if you're skilled and essentially impossible for a beginner. However if you have pretty much no way to get those, or if you want a challenge, you could try replacing the entirety of the connector with small gauge magnet wire (the same stuff as enameled headphone wire).
Well, if it's not the connector portion that's torn, you might get away with trying to repair the traces with some solder paste to some wires, but otherwise, yeah, it's a pain.
Ha-ha, good luck drawing >10 lines with <0.5 mm pitch with solder paste, silver pencil or whatever :D
Well, not all of them are that small. ;) I've seen some with as much as 1/8" spacing.
ron.rico1 year ago
if you want someone to do this for you-- try www.microconnex.com 425.396.5707. they do a good job and offer quick turn protos. they can be somewhat spendy-- but you typically get what you pay for... good luck and thanks for the article on "DIY-flex-pcb" !
megg2 years ago
great instructable! just wanted to say that i learned how to do this last week and we used acetone and a soft brush to clean the remaining wax off the etched board.
dasraiser2 years ago
would it be poss'ible to convert an old HP cartridge to carry liquid wax? as the heads use a thermal jet system.
bsm1th2 years ago
Xerox ColorQube 8570, 3 mil kapton with 2oz copper. Worked great straight out of the box. On my first try some of the 0.3mm traces were eaten through a little too much but I guess that's what I get for not measuring out the HCL and H2O2. Thanks!!!!!
I got the film and the solid ink printer, but I have a problem. Do I need to clean the pyralux or something because I am having a hard time soldering on there? I mean is there a coating on there that is not letting me solder it. After I print it and cleaned it with some acetone for the ink, do I need to clean the wax some other way. I tried with the rubbing alcohol but it seems to take the copper off with it? Any suggestions?
Also note that it would be a good idea to use DeoxIt or similar product to not only clean any potential residue from the circuits on your shiny new PCB, but to also protect it as well, this is an important step.
far1.k3 years ago
Flexible copper clad laminate is sold on eBay.com. Just search for "Pyralux". I have just received some sheets and I'm going to try this instructable.
sfcircuits3 years ago
The Xerox Phasers are excellent for this the printing since they use wax for the printing, providing a good quality resistance for the etching.
SpiffyChee3 years ago
Ok. So seriously. How in the world can i buy this dupoint paralux stuff? The internet is not helpful. Samples are not available for a long time... I contacted dupoint already.
I just found it on eBay, single sided 2oz 9''x12'' for ~6$. Just search for pyralux. Nice tutorial btw!
illica3 years ago
Has anyone had experience with CuNi 715 (~6mil)...it's a Copper Nickel alloy... hot pressed onto Pyralux LF0110 or FR0110?
zack2473 years ago
this is really cool! do you think print shops could have solid ink printers? then i could just ask them to print to the copper sheet right?
jorbe23 years ago
Sorry I want to add this link:

http://www.taiyo-america.com/products-cc.php

This is the right solder mask product for flexible PCBs.
jorbe23 years ago
hi guys, my first comment on instructables:

you can find the pyralux at insulectro.com:
http://insulectro.com/index.php?page=58#

I'm not sure if we can use a solder mask (PSR-4000 BN) with this material:
http://www.taiyo-america.com/products-LPI.php

After solder mask try:
Solder paste & the skillet method, check kapton temps first, I'm not sure about this.

:)
kingbowser3 years ago
on ebay you can easily find single side and double side copper clad FR4s in a very thin fashion. For example now (08/09/2010) there are various auctions of 0.005", 0.0063" and 0.0075" (or even thicker, it depends from what you are looking for...) available from different sellers. Those one are flexible, even if they're not made by mylar film.
A copper clad FR4 is definitively much more simple to find than pyralux, but obviously the performances won't be the same.
Unpaid_OT3 years ago
If you want to generate flex PCBs you should check out a new flex PCB product called Protoflex www.protoflex.net. They make pre-cut flexible PCB IC adapters (SOIC, TSSOP, SOT etc.) with an adhesive backing. Just paste them on to build your circuit. They work pretty cool.
ARJOON4 years ago
hey for the etching for those who did not get the ecthing solution. electrolysis can be carried out. very cheap and easy
(removed by author or community request)
when u've already done the toner transfer You just have to put it in salt water. connect one end to a nail. and another end to the board. i forget which one should be anode or cathode just see this and you will understand. http://en.wikipedia.org/wiki/Electrolysis but you must monitor it very carefully because it can go under the tone also
You can use other solutions (etchants) to remove the copper from the substrate as well. A good alterantive is Cupric Chloride - here are a couple of available compositions commonly encountered;

CuCl2
 - Cupric Chloride Anhydrous
CuCl2 2H2O - Cupric Chloride Dihydrate/Dehydrate

See this Instructable (link) which explains a simple method of accomplishing the etching process...

http://www.instructables.com/id/Stop-using-Ferric-Chloride-etchant!--A-better-etc/step6/Alternative-overly-complex-Method-Make-Cupric-C/ 

Also check out the comments section, as shaunak has some advise on a good variation of this method.

Please remember to dispose of all hazardous materials in a safe, responsible and environmentally friendly manner.

Credits to those referenced above who are an asset to our community!

 
Does anyone know where I can buy some pyralux? I requested some from the dupont website but no answer?
avatar_2234 years ago
I just got my hands on a Xerox Phaser 8550.  I was very excited about getting some circuits printed, but the printer is a bit of a disappointment.  It seems that the wax is printed on a drum and then press up against the PCB. unfortunately the  wax seems to like the drum more than my pyralux and leaves half of my board in the printer.  Does any one know what model the author is using? Any suggestions?  
tarts4 years ago
Hello Do you think that this solid-ink-printer will also work with regular PCB-s, if modified to accept flat plates?
Foxtrot70 tarts4 years ago
Hello - I had just seen an other Instructable dealing with same process on PC boards. I have two spare spare printers and I am considering doing the same thing. It seems that the various door switches can be defeated and the pinch bar for the paper can be adjusted for board thickness. This would make life a lot simpler when doing a project.
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