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View Full Version : How to etch a PCB using blue press and peel film from Jaycar Electronics.



DrNomis_44
23-04-2017, 08:39 AM
Hi Everyone,

Thought I would start a thread on this topic, since I have had some experience with it, anyway, most people getting into building DIY pedals will, at some stage, want to have a go at making, or etching, a proper PCB, or Printed Circuit Board for their DIY pedal builds.

So, for starters, what is a Printed Circuit Board and why do we need them?, a Printed Circuit Board consists of an insulating material which has had a thin sheet of copper foil glued to one or both sides of it, the insulating material can be made from phenolic (a mixture of phenolic-resin and paper pressed together under high pressure), fibreglass, or even ceramic, in the early days of printed circuit boards Bakelite was even used too, the thin sheet of copper foil glued to one or both sides of the insulating material, in the case of double-sided PCBs, is just copper that has been flattened out so it's very thin, about the same thickness as aluminium kitchen foil, copper is used for two reasons, firstly it exhibits relatively low resistance to electricity, secondly it can be easily soldered to.

The copper foil is used to form the electrical wires that join electronic parts together to form an electronic circuit, this is done by using a special chemical, called an etchant, to dissolve, or etch-away the unwanted parts of the copper, the wanted parts of the copper are protected from the etchant by coating them with another special chemical, called a resist because it resists the the chemical etching of the etchant, there are two main chemicals used as an etchant, one is called ferric chloride, the other is called ammonium persulphate, personally, I prefer to use ammonium persulphate since it is less messy and easier to deal with than ferric chloride, both etchants produce about the same results.

Once all the unwanted copper has been etched away by the chemical etchant, small holes for the electronic parts leads are drilled through both the copper foil and the insulating material, and then the parts leads are soldered to the copper foil and trimmed.

The reason for using PCBs to make a DIY pedal is that it neatens things up, it also reduces the possibility of wiring errors and saves time.


Years ago, if you wanted to etch a Printed Circuit Board, you had to buy a lot of expensive equipment and chemicals, and have access to a photographic dark room, in the 90's, some clever people worked out that you could produce Printed Circuit Boards of usable quality, at home, with a computer, a laser printer, some specially designed plastic film, the PCB artwork, chemical etchants and a small etchant tank, and a standard domestic electric clothes iron, you no longer needed to have access to a photographic dark room, all you needed to do was to print the artwork onto the film and then transfer it onto the copper foil before etching, this relies on the fact that the black toner powder used in laser printers softens when heated and it adheres to the surface it is printed on, furthermore, it was discovered that the black toner powder worked very well as an etchant resist as well.

As it just so happens, Jaycar Electronics stock both the chemical etchants and something called blue press and peel film, I just checked my Jaycar Electronics catalogue and they do indeed stock blue press and peel film, the catalog number is HG-9980, I used some to etch a PCB for my Univibe pedal and I got pretty good results.


As Andy40 has demonstrated in another thread, you don't necessarily have to print the PCB artwork onto press and peel film, you can also print it onto a sheet of paper from a magazine, and still get very useable results.

DrNomis_44
23-04-2017, 10:55 AM
Rightio, so now we have a bit of an idea of what a PCB is and why we need one to make a DIY pedal, how do we go about making a PCB?, to make a PCB we need the following things:


* A computer of some sort, can be either a Mac or a PC.

* A functional Laser printer, Inkjet printers won't work for making PCBs using the press and peel toner-transfer method, unless they use specially designed ink cartridges.

* A suitable image of the PCB artwork.

* Press and Peel toner-transfer film, or some old magazines, the ones with glossy paper seem to work best.

* Blank un-etched PCB.

* Ammonium Persulphate Etchant, you can buy both the press and peel film and etchant from Jaycar Electronics, the Ammonium Persulphate etchant comes in the form of a white crystalline powder which you dissolve in warm water.

* A non-metalic container of suitable size that you can use as an etchant tank, it needs to be big enough so that the PCB being etched can be submerged copper-side up in the etchant.

* Newspaper, or spare sheets of A4 printer paper for wrapping the PCB in prior to ironing.

* A standard domestic electric clothes iron, you might be able to buy a second-hand one from your local Cashies store.

* Small centre-punch.

* Set of thin drill bits for making PCBs, Jaycar Electronics may have some suitable ones in stock.

* Small vertical drill-press, or you can manually drill component-lead holes using a pin vice (Jaycar Electronics stock these).

* A can of PCB lacquer, used to protect the copper foil tracks and stops them from corroding away, PCB Lacquer can be soldered through.

* Masking tape.

* Fine steel wool.

* Ajax cleaning powder.


Method (assuming that you're using the blue press and peel film):


1, Decide on what pedal you are going to build and go online and download the pdf files if there are any available, these usually include the PCB artwork and build instructions, etc.

2, Print the PCB artwork onto the press and peel film, or magazine paper, using the Laser printer and your computer, ensuring that you've got the artwork oriented correctly, usually the artwork pdf will have been scaled correctly so that it prints out at the correct size.

3, Once the artwork has been printed out, clean the copper foil side of the PCB with the fine steel wool and Ajax powder under running tap water, the idea is to clean off any contaminants like grease from fingers that will prevent the printer toner from sticking to the copper foil, using the steel wool, burnish the copper foil so it's bright and shiny.

4, Carefully dry the un-etched PCB with a dry towel or some toilet paper.

5, Place the PCB artwork on the PCB so that the toner is in direct contact with the copper foil, making sure that the artwork is centred within the PCB material (it helps to cut the PCB material a bit larger than the artwork).

6, Wrap the rest of the press and peel film around the PCB material, using masking tape to hold it in place.

7, Next wrap the PCB material and film in a layer of A4 printer paper, or newspaper, make sure you note which side has the artwork on it.

8, Using the electric clothes iron, apply heat evenly to the side that has the artwork on it, the printer toner-powder will soften and stick to the copper foil, make sure you read the instructions supplied with the press and peel film since the instructions will tell you what temperature to set the clothes iron to and how long you need to apply heat for.

9, After the heat has been applied for long enough, let the PCB material cool down, once it has had time to cool, carefully remove the paper and film wrapping, you should be left with the printer toner powder adhering to the copper foil.

10, Fill the non-metallic container half-full of warm water, and dissolve the recommended amount of etchant powder in the water, the recommended amount should be printed on the container that the etchant powder came in, be careful not to add too much etchant powder to the water otherwise it'll etch away the wanted copper protected by the printer toner, had that happen a couple of times while trying to etch a PCB, using warm water will speed up the etching process.

11, Place the PCB copper foil side up in the non-metalic container with the etchant, it might take a little bit of time for the etching process to start, you'll know that it has started when you see small bubbles forming on the copper foil, you can help the etching process along by gently agitating the etchant.

12, Once all the un-wanted copper has been etched-away by the etchant, remove the PCB from the etchant and pat dry with either a towel or some toilet paper.

13, Once the PCB is dry, clean off the printer toner with the steel wool so that it's all shiny again, then mark the centres of the component lead holes with a centre-punch and drill them out to size using the thin drill bits.

14, Finally trim the PCB to size and spray the copper foil track side of the PCB with the PCB Lacquer.

15, The PCB should now be ready for soldering-in all the electronic components.


Note: It might be better to lacquer-spray the copper foil side of the PCB after etching and removing the black toner, before centre-punching and drilling the component holes.

Andy40
23-04-2017, 02:00 PM
Thanks Doc. I wish I read this before I drilled mine. I did look at the Jaycar clear film but its expensive, I think $35 for 5 sheets? but I haven't had great transfers with magazine paper, maybe i should try it. Also what program do you use to draw out the PCB?, there wasn't one with the greenbean pedal and I'll have to draw one out.

DrNomis_44
23-04-2017, 02:15 PM
Thanks Doc. I wish I read this before I drilled mine. I did look at the Jaycar clear film but its expensive, I think $35 for 5 sheets? but I haven't had great transfers with magazine paper, maybe i should try it. Also what program do you use to draw out the PCB?, there wasn't one with the greenbean pedal and I'll have to draw one out.


One program that I can think of off the top of my head is a bit of software called DIY Layout Creator, it's open source software so it's free, if you register yourself as a member at Freestompboxes.org, you can download it from one of the forum threads, I think if you just google DIY Layout creator you should be able to download it that way, there is a bit of a learning curve with it though, but the good thing about it is that you can do Veroboard layouts with it as well, I'll see if I can find a download link.


Here we go, here's a link to a website where you can download DIY Layout Creator:

https://github.com/bancika/diy-layout-creator


Yep, the press and peel film is a bit expensive but you do actually get about 5 sheets of it per envelope if my memory serves me right, most of the project pdf files that Madbean has on his website should have a page with the PCB artwork on it, to be honest, it's been some time since I last etched a proper PCB so I mostly use Veroboard to build my pedals, I should get back into etching PCBs.


Here's another download link for DIY Layout Creator:

https://github.com/bancika/diy-layout-creator/releases


You might also need to download this file if you're installing DIY Layout Creator in Windows 10:

https://www.java.com/en/download/win10.jsp



Update:


I downloaded the DIY Layout Creator windows executable file from the second link, plus the Java Runtime environment file and installed both on my laptop computer which is running the 64 Bit version of Windows 10 Creator's Update, and I can confirm that the DIY Layout creator software seems to run fine so far with no issues, I don't know whether it'll run fine on the latest Mac OS X though, can't see why it shouldn't since it's supposed to run on any platform that supports Java.

Andy40
23-04-2017, 03:53 PM
Thanks Doc.

DrNomis_44
23-04-2017, 04:01 PM
You're welcome Andy40.