How to Make Your Own Circuit Board Devices

Printed circuit boards (PCBs) allow engineers to create permanent electrical circuits that consist of multiple components and are capable of complex functions. Each board starts as a thin sheet of fiberglass with one side coated in a layer of copper foil. The surface is then etched with a strong acid, leaving only the circuit paths and terminals. Once holes for the circuit components are drilled into the board, a technician carefully solders each into place. Most manufacturers use expensive, automated machinery to produce PCBs; however, electronics hobbyists can become proficient at etching and soldering their own PCBs.

Difficulty: Moderate

Instructions

Things You'll Need:

• Computer
• Printer (inkjet, laserjet or bubble jet)
• Black felt-tipped permanent marker
• One 8 1/2- by 11-inch sheet of Press-n-Peel blue transfer film
• Ironing board
• Iron
• Copper-clad sheet of PCB (one-sided)
• Glass container (must be large enough to hold the entire PCB sheet)
• 1 liter of muriatic acid (~31% hydrochloric acid)
• 2 liters of hydrogen peroxide
• ExpressPCB software
• Electric drill
• 0.94 to 1.04mm PCB drill bit
• Acetone (or nonacetone nail polish remover)
• Electric soldering iron (15 to 30 Watts)
• Coil of 1.6 mm solder with a flux core
• Paper towels
• Protective rubber gloves
• Safety goggles

Printing Your Circuit Diagram

1. Download and install your free copy of ExpressPCB (see Resources). It is a freeware application designed especially for creating printed circuit board devices.

2. Design your circuit. Make sure that your circuit diagram will fit onto the copper-clad PCB sheet you purchased and that it is no larger than 8 by 10 1/2 inches. Then run the "Check Circuit" program (found under "Tools") in ExpressPCB to catch any errors.

3. Print your diagram on the dull, emulsion side of the Press-n-Peel transfer paper.

4. Lay the copper-clad PCB sheet on the ironing board, copper side up. Place your Press-n-Peel sheet containing your printed diagram with the dull, emulsion side down on the copper-coated side of the PCB sheet. At this point, the glossy, nonprinted side of the blue Press-n-Peel sheet should be on top. Set the iron at the highest temperature (do not use steam). Once the iron is fully warmed up, gently set it onto the center of the Press-n-Peel sheet. Let it sit for about 3 minutes. Then gently lift the iron and place it carefully on another part of the paper for 3 minutes. It's okay if the iron overlaps in some places. Repeat the process until the entire surface has been heated.

Etching the Circuit

5. Let the PCB sheet cool for about 3 minutes. Then take the corner or edge of the Press-n-Peel and slowly peel it away from the copper-clad sheet.

6. If the ink did not transferred completely to the copper surface, fill in the trouble spots with the permanent marker. The hydrogen peroxide/muriatic acid etchant solution is hydrophilic, meaning it will dissolve copper ions but not nonpolar substances like permanent marker and ink. Therefore, the etchant solution will dissolve away all the copper coating except that which is covered by the nonpolar ink and/or permanent marker.

7. Put on rubber gloves and safety googles. In a very well-ventilated space, pour the hydrogen peroxide into the glass container. Then slowly add the muriatic acid.

8. Once the permanent marker (if you used it) has dried, slowly immerse the PCB sheet into the etchant solution. After 20 seconds, gently dip the sheet repeatedly until all exposed copper dissolves. When all the copper is gone, remove the sheet and rinse it under running water. Blot dry with paper towels.

Preparing the PCB for Soldering

9. Pour a few ounces of acetone (or acetone-free nail polish remover) onto a folded paper towel and vigorously scrub at the ink until only copper remains. Let the PCB air dry for about an hour.

10. Using the spacing and hole measurements from ExpressPCB, choose a high-speed drill bit with the same diameter as the etched-out space at each component terminal. Because of the relatively small diameter of the drill bit, there is a chance it could break off. To prevent this, position the bit as close to perpendicular as possible.

11. Drill all holes. Then install the components through soldering.

Tips & Warnings

• The ExpressPCB software has display options such as "Screened Outline," which overlays the circuit diagram with outlines of the area each component will occupy in the final product. Make sure that this option is turned off when you print the diagram. Soldering strategies and techniques vary widely depending on specific circuit structure, voltage and component properties. See the link in Resources to determine the soldering methods best for you. Use a soldering wire with a flux core. Be sure to heat the component wire, not the soldering wire. All components feature long, rigid wires at their terminals. For them to work properly, the solder must be melted by heat absorbed through these wires, not directly from the soldering iron.
• Handle the PCB sheet very carefully after ironing. It will be very hot.

Resources

• Soldering Techniques
• ExpressPCB