Archivo de la categoría: PCB DESIGNING

DESIGN OF A PCB USING CNC

In this tutorial I’m going to show you how to make PCBs using the CNC milling machine. First of all, we need to know what is this machine.

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DESIGN OF A PCB BY PHOTOLITOGRAPHY

In this tutorial I’m going to explain how to make an electronic board using photolitography with acid.

It’s very important to take much care because we are going to work with very corrosive and toxic substances, such as hydrochloric acid, so we need to work in an appropriate place conditioning to remove gases. Also we will need some containers to fill with the chemical wastes and a water tap close to the working area.

seguridad

 

It’s very important too to noteworth the light, that should be developing photographic light.

Now, and obeying the above requirements, we can start printing the photolitycs previusly designed in Proteus.

Imagen

For that, we just need a printer and follow the next steps in the PCB Layout window: just click in Output>>Print Layout and choose the printer. Here you can also configure some parameters like the layouts you want to print, the scale, the rotation and reflexion, etc.

Imagen1

Now we can continue with the etch process, which is the next step. First we have to have bought a PCB cupper board:

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As can be observed in the image, have a positive photosensitive double sided board. The material is fiberglass, and has a thickness of 1.5mm. 35 micron copper.

Once you have analyzed the copper board, we will cut the size needed, with the dimensions of the printed and photolithography, we have had to remove the protective plastic with adequate lighting so that the same fogging occurs.
This done, the next step is the placement of photolithography in the plate.

If double-sided would have to make a sandwich with fotolitos candling and taking accurate measurements, because it narrowly descuadre us, our work go to waste.
Another option you have is if you have a milling machine or Bungard, making drill and then place the lithos.

bungard

Once we have placed the lithos, had to own sunshine itself. For this we need a machine exposure unit, as seen in the image. It is a machine that emits ultraviolet light, and say that while insolation is our fotolito is transmitted to the copper plate. This machine also has a vacuum system to prevent the plate from moving or photolithography. The minimum exposure time is 350 seconds.

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The next step is the developing process, in which is already necesary to use chemicals. The mission is to make developer liquid leftover after insolation varnish plate is removed, leaving only the copper that is then attacked. Mainly consists of a solution of caustic soda in water.

After the process of heatstroke, we will make the development of the plate. To do this we will take a bowl or plastic container, and we have to pour over the same liquid developer.

We introduce the plate in the solution and begin to move the tray gently until we see our circuit drawn in the PCB form a more obscured.

Now we start with the process of attack. First of all, we take the substances we need, which are three: hydrochloric acid, hydrogen peroxide (110 vol.) and water.

acido

These three substances will mix in another bowl pouring 33% of each.
Acid attack all the excess copper, and the darkened tracks are under the glaze takes longer to be attacked, leaving our copper tracks.

Here you can see an example of the process of acid attack.

ejemplo

It is important that while the plate is being attacked, with tweezers, pulling the plate go every so often and washing under running water to observe when the process has finished, as if we need more time, you can damage our tracks.

Once the process is complete will wash and clean up our plate. If necessary we can make a light sanding. Finally if we had made ​​the drill, that would be the last part, before moving on to solder our components in the PCB. If we have much better varnish, we can give a light coat of spray varnish for us to be much more professional, so yes, if we have to put roads, roads first and then varnish. Finally, we can solder components on the solder side.

Here is an example of a PCB in the solder side:

placa_soldadura

And here you can see the result in the component side:

placa_componentes

Thought to be over … but we used chemicals residues highly polluting, which can only be disposed of at sites established for this purpose, as a collection point. In our case the waste is accumulated in carafes and containers, so that when we take enough, will pick them up to discard.

The following containers store the liquid developer.

recipiente

This carafe accumulate acid, after being used. It is very important to label the contents to avoid unnecessary risks.

garrafa