Making Printed Circuit Boards

How can you make a professional looking PCB in an unprofessional way?

Basic Tools

You'll need some basic tools like a ruler, a pencil, a softtip permanent marker, scotch tape or masking tape, hacksaw for cutting PCBs to size and a plastic basin for etching the board. A fluorescent lamp shade and a clean, clear sheet of glass (preferably the thick heavy ones on table tops).

The not so basic tools are: computer running Windows and a good quality printer, preferably laser so you can print directly to acetate (transparency film for overhead projectors). You'll need a very good software for making your designs like EAGLE. A drill comes in very handy, preferably a really good power drill from Bosch or Black & Decker.

A word of advice: dont economize on a cheap brandless drill, chances are, you'll be very disapppointed. I've bought one before and its rotating shaft was not aligned properly so every drill bit I used got bent. Drill bits are very expensive. You can buy bits 10 pieces a pack at Deeco for 110 Pesos. Just add a few more bucks and get a branded one from a reputable hardware shop and besides, power tools are a good investment.

Designing Your Layout

Cadsoft makes EAGLE Layout Editor and you can use it as freeware (everything working) but you are limited to a board 3.xx inches by 3.xx inches in size. If you register you'll be able to make unlimited sizes so they say. Its very easy to use.

Design your schematic and then EAGLE will automatically make the connections on the board layout. All you have to do is to place the components inside a given area then click the AutoRoute button and presto! You can make simple or very complex designs with this program.

Visit CadSoft's website and download their wonderful software.

But its not that simple, really!? There's still some trial and error involved when routing your wires from your design. Careful planning from the start can save you lots of time and effort. Always try to minimize your component count on the board. Routing your wires is very time-consuming. A fast computer will be extremely helpful for those of us who are impatient with results.

It is advisable to add some text on your PCB design so you can easily determine the positions of the components. Also, it is easier to identify the orientation of your design. Text makes it even look more professional.

After you've finalized your design, you can print the board design directly to acetate if you have a laser printer. If you have the special acetate for inkjet, you can use it but the result will not be quite as good as laser-printed or those transferred from acetate via copier.

If you only have an inkjet, you can use ordinary plain white paper and make sure you pressed the Black option in the File . . Print menu. This will give you a solid black print out and now you can run to your nearest business center and have them transfer the design to acetate. Be sure that they offer powder copies for best results.

What You'll Need To Buy

Now that you have your design in acetate, you have to go and buy three things: a presensitized PCB, a developer, and ferric chloride.

Fig. 1 (Presensitized PCB Package from Alexan)

The presensitized PCB comes in many sizes from a 4" X 6" to 12" X 18" and the smallest single-sided board costs about 50 Pesos. There are also double-sided versions of the available sizes. Compared to ordinary PCBs, the price is to steep but considering the quality you'll get from using the presensitized version makes it really worth it. First thing you'll notice is the bad odor when you open the package but never mind that. The copper side of the board is covered. A white sticker covers the copper side, this is to protect the sensitive part from exposure to light.

You'll need two chemicals: a developer and ferric chloride. The developer costs 25 Pesos per pack. It also available from Alexan. A single pack will need to be dissolved in one liter of water. The resulting solution will be used to "develop" the exposed board (this will be explained later). The ferric chloride will be used to etch the design imprinted on the board.

You can get the ferric chloride from Deeco, they sell a very strong solution ideal for fast etching. The shorter the time the board is submerged in the ferric chloride solution, the better.

Transferring The Design

Mark the PCB, using your ruler and a pen or pencil, according to size and cut it with the hacksaw. Remember, do not remove the protective layer (sticker) yet when marking or even after cutting the board.

Figure 2. (2 pieces of cut PCB with protective layer and Acetate)

Now that we have a board, we proceed to transferring the design from the acetate to the board. Prepare the scotch tape, the sheet of glass and the fluorescent lamp shade.

Place the acetate face down on a table or any flat surface. Remove the sticker from the board and place it on top of the acetate with the copper side on the acetate. Use the scotch tape to hold them together.

Turn the lamp shade on and place the acetate with the board beneath it. The copper side of the board must face the light. Make sure that the gap between the lamp and the board are 5 centimeters only. Place the glass sheet on top of the acetate to make sure that it will lay flat on the board. Wait for ten minutes.

Figure 4. (Exposing the PCB)

While waiting, prepare the developer solution. Use one liter of water to dissolve the developer. Shake and stir it very well. Store the solution in a container which can be sealed so you can use it again. You'll only need to use a fraction of it for developing small boards. Use the plastic basin for developing your board.

Figure 5. (Mixing the developer with water)

After ten minutes, take the board and remove the acetate. If you will look closely, you will see blurry green lines on the copper side of the board. The patterns are similar to the design on the acetate. Now you will have to remove the exposed parts of the board by immersing it into the developer solution. Immediately, you will see that the exposed parts are coming off the board leaving only the green lines. You must not let the board be submerged for longer than two minutes in the solution because it will damage your design and you will have to do it all over again. Shake the basin side ways for faster results.

Figure 6. (Developing. PCB on developer solution)

Now the image from the acetate is clearly imprinted on the copper side of the board. Use running water to wash off the remaining residue off the board. Check if there are any errors because this is the only time that you can correct mistakes. Use the permanent ink marker to connect broken lines.

Figure 7. (Developed PCB. Ready for etching.)

If you're sure that everything is ready, you can now use the ferric chloride to etch your design.

Finishing Touches

Use the plastic basin for etching the board in ferric chloride solution. The solution will remove all excess copper (the ones that are not green). After a few minutes (about 15 minutes or so), after all the excess copper are gone, you can now wash your design using water and now you're ready to drill the holes for the components.

Make sure that the drill bit that you're going to use is exactly the same size or smaller than the marker on the board or else, figure it out...

The green stuff over the lines are not conductive, you have to remove (by scratching) them before you can solder anything over them. You can use sandpaper to remove the green lines or use any sharp object to scrape just the area where you are going to solder.

Dont over do the soldering process because it will surely damage the component and the board.

revised 07-05-2002

orig 06-12-2001