Integrated Circuits development with Toner transfer and with the aid of high temperature silicone

circuito impreso.

Introduction

In this article, we'll explain how to make integrated circuits of single or double layer, with the help of sheets wet with high temperature silicone
Normally the toner transfer method is used with magazine sheets or glossy paper, but our practical results are not optimal, because the toner quits from paper with a lot of difficulty, and also in the last stage the cellulose adheres to the copper clad, and the cleaning is very time consuming.
If we add silicone to a sheet of paper and print a circuit with the laser printer, the toner doesn't go out completly fused, so it's very easy to transfer this toner to the copper clad of the PCB.
Also this silicone paper can be reused as many time as you want.

We get a normal sheet and put it in a clean and smooth surface, because any irregularity will mark the paper.
With a spatula we'll extend a fine layer of high temperature silicone (of two that i tried, the best results are with the brand Ceys).

high temperature silicone.

Despite the sheet can be reused, it's a good idea to make all papers that we can, so we spend all the silicone because it is highly probable that it will dry over time. After that, we let dry the paper 24 hours.

We extend the silicone with a spatula.

We print the circuit we want to perform on the silicone sheet (obviusly on the face that there are silicone).

Laser printer we use to print the paper.

Before printing the circuit, we must bear in mind that if you want to make double-sided circuits, they have to be focused the two sides. We have a simple and accurate enough (let's see if someone improves it). It consists in drawing two normal lines in the corner of the project, this lines must be as thin as can be.

We draw the normal lines to align the sides.

The copper clad must have a perfect made corner, in order to align the two sides (we mill it to get more precission).
The surface must be clean, we'll get it done with a little acetone and then glass cleaner that removes the surface pressure.Once cleaned and dry, we prepare everything for the transfer of the toner from the silicone to the copper clad, because once you focus the paper we won't be able to release it.
We place the paper printed on the table with the toner upward, and put the copper clad on top of the paper by matching the corner with the good corner drawn.
We take it carefully so as it can not move (we can also use a clip or something that holds it) and we put it throgh the laminator. The laminator we use is from a photocopier, we have had to widen it slightly to fit the copper clad.
Any roller should be fit for this job, the ideal is a laminator used to plasticise documents.
With our technique is not necessary that this rod be hot.

photocopier fuser

We remove the plate all we can, without getting out completely.
We take a heat gun and put the accessory that makes the air distributed to the width.
With one hand we endure the sheet and with the other we heat a little the copper clad in the side we want to transfer (10 sec) by distributing heat across the surface, and finally with the gun pointing towards the pressure rollers, between the board and paper,

Then we pass the board through the roller at normal speed uniformly, if the roller is not motorized you'll have to be helped with this step. We must ensure that the paper did not touch the gun or the plate before passing through the roller because it would fuse too early.

We heat the board and pass it through the laminator

Once we have passed across the board through the roller, immediately remove the paper before it gets cool. You will see that the whole toner is now on the copper board. You can clean the silicone paper with acetone to remove the remains of toner and reuse hassle-free.
If you have to do the other side, the process is the same, only we must take care not to heat the plate too hard, because we could fuse the other side toner, that is in direct contact with the roller and could get blured.

Circuit with the toner tracks.

It is time to put the copper clad in acid. We use ferric trichloride.
You must be careful handling with acids. Although this is not the more dangerous one it is an acid.
This operation must be performed in a well ventilated place, using gloves and safety glasses.
Remember that acid eats anything metallic. We get a plastic bucket that can be closed and be kept away of children or people not allowed to handle this nasty stuff.
Add distilled water and introduce a 40% acid.

Acid ready to eat copper.

We can leave the plate sumerged and take it out when no copper is visible, but there exist the danger of desappear the thinner tracks because of under etching.
The best thing is to keep moving the board inside the acid, and even better if we can introduce air bubbles inside the bucket.
With these methods it takes less and the tracks are better shaped.

Copper clad after 10 minutes.

After 15 minutes.

Finally in 20 min. it's ready.

These times are moving the board with a 40% acid saturacion.
After taking out the copper board, it must be cleaned with water to remove the residual acid, and then we remove the toner with acetone.

Cleaning the board.

This is a double-sided PCB and must be drilled. I put the drill with revolutions, 2000 rpm for a drill of 0.9 mm and performing very well, more rpm would wear excessively the drill because of the abrasiveness of the fiberglass.

Drilling the board.

Drilled board.

We hope this article is useful for you, if you have any doubts or comments, comment them here.

Greets