Befaco.org

PCB printing tutorial

DIY method for producing PCBs (and front panels) at home

This tutorial is an update of the construction tutorial published by David Pello in 2008 at http://ladecadence.net.
We have completed this with our own experience, obtained through the development of prototype modules that you can find on this site. This method is equally as useful for printing circuits as it is for printing frontal panels.

To begin, I will tell you the tools that I use for the fabrication of PCBs with this method, I don’t think I have forgotten anything:

The first step is to cut the board to the size of your design, for this you can use a hacksaw and a press to hold it to the table. If you don’t have this, you can press a box cutter with force across the lines on each side until the PCB matches the marks.

After it is cut to size, sand the sides so that they are smooth and without burrs. Then, with the scouring pad, scrub the surface a bit to polish it and remove the chemicals used to make the board… this is important because if not done, the toner will not adhere well to it very well.

Now, print the design using the laser printer and photo paper, but keep in mind that the image will be inverted on the PCB. Print the same number of layouts as you will have for components, or the two sides if you are doing a two-sided PCB.

These are the papers we have tested that work best:

The majority of photo papers don’t work for this method, and in general the more expensive, the worse. Keep in mind that if you do this with another brand and it doesn’t work for you, this is probably why.

Now, cut the design to fit the face of the PCB. Make sure that everything is clean and dry before ironing.

Now, iron the design to the PCB. It is critical that you make sure that you iron without steam. Iron smoothly but firmly, starting at a corner, working your way around the rest of the board, making sure that you don’t leave bubbles, you will see when it is completely attached to the board.

There is no fixed time, but iron until you see that all of the PCB diagram is attached to the board… It could be a minute or less, the size of the board is relatively proportional to the amount of time that needs to be spent.
I like to put pages of a magazine under the PCB so that I can forcefully iron with two hands without worrying about sliding the PCB around on the table.
After it has been ironed, put it in the “tupperware” container to soak in warm… in my house, keeping it on until the stop produces warm enough water.

You will see how the warm water is starting to detach the paper from the PCB. If you leave it in for five minutes, it will be completely detached. After some time, loosen the paper, and take it carefully out of the water.

It is possible that some traces did not stick well, and were loosened while it was soaking… if you look at the photo, in the top-left corner some of the drawing did not transfer. You can clean off the PCB and try again, but there is another solution. If not very much is ruined, and it is an area that does not require fine detail, you can re-draw it with a fine-tipped permanent marker, like those you would use to write on CDs.
In this board, I had to do this “hack”.

Now, put the PCB in the etching compound.

Typical etching compounds are:

I prefer the second because it is very cheap (although it is more a matter of preference). The normal proportion is one part HCL for two parts of a 50:50 mixture of 110 volume Hydrogen peroxide and water. If you can’t find 110 volume Hydrogen Peroxide, you can use 40 volume Hydrogen Peroxide (the type for bleaching hair), if you use the 40 volume, don’t add water.

WARNING: never do this inside of a house, it is necessary to do this in a well ventilated place, never breathe the vapors that come out of the etching compound. If by accident you touch the compound go ans splash you hands fast.

It is impossible to say the exact amount of time it will take, but you will see when it is done, as the etching compound will have dissolved all of the visible copper. When this happens, take it out and rinse it :) . If you take it out and see any reflection, there is still a part that needs to be etched away.
This is fine, you can put it back in the etching compound.

If you think that the reaction is too quick, the mixture can be diluted with more water.

Now, for the drilling. I use a cordless drill… the ideal is a Dremel with a fixable base, but you can also do a perfect job freehand.

To do the final finish, also to help with mounting, you can apply a silkscreen to the face of the PCB.

For this, align the impression with the drilled holes and repeat the ironing and immersion process, but only in warm water (not the etching compound!!!! :) ).

To do double faced PCBs, use the same method… first transfer the toner to one side, and drill three holes into the board (where there will already be holes, anyway), and use those holes to align the other side. After doing this, transfer the image. When both are ironed to the board, put in warm water again, remove the images, put into the etching compound, turning occasionally.

 

Now, some people use acetone or another solvent to remove the toner, but I simply use a metal

scouring pad. It’s good practice to remove the toner after drilling, because while scouring to remove the toner, you are also removing the burrs produced by drilling, which makes it easier to solder.

Now the PCB is ready. It should look something like this:

The PCB is ready to mount… before beginning to solder it, it is best to examine it to see if there is continuity between all of the traces, it is best to use a voltmeter to do this, as doing this saves trouble down the road when trying to populate the PCB.

Now… solder it!!!

 

 

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