How to DIY PCB Board Etching?

Introduction

Printed circuit boards (PCBs) form the backbone of all electronic devices and products we use. From smartphones to appliances, PCBs provide the mechanical base and electrical connections for components to be mounted on. While PCB fabrication has largely shifted to professional PCB manufacturers using advanced processes, etching your own PCB boards at home can still be a fun DIY project.

PCB etching involves selectively removing copper from a copper-clad board to leave only the desired copper traces on the board. This article provides a step-by-step guide on how to etch your own PCB boards using simple DIY techniques.

Overview of PCB Etching Process

The PCB etching process typically involves the following key steps:

1. Design the PCB Layout

• Create the schematic diagram for your circuit using EDA software.
• Convert the schematic to a PCB layout with component footprints and routing.
• Finalize layer stackup, board dimensions, silkscreen, etc.

2. Print the PCB Layout

• Print the layout on a laser printer using a toner transfer method.
• Or use a direct inkjet PCB printer to print the layout.

3. Prepare the Copper Board

• Cut a copper-clad blank board to the required size.
• Clean and prepare the board surface.

4. Transfer the Layout

• For toner transfer – Iron the paper printout onto the board to transfer toner.
• For inkjet – Layout is directly printed onto the board.

5. Etch the Board

• Immerse board in etching solution to remove exposed copper.
• Agitate the solution to expedite etching.

6. Drill Holes

• Drill holes for component leads using a small PCB drill.
• Deburr holes to remove roughness.

7. Finalize the Board

• Remove toner/ink using acetone.
• Scrub off etching residue from copper traces.
• Apply solder mask, silkscreen markings etc.

The actual steps may vary based on the specific methods and materials used. But the general process remains the same. The rest of this article will examine each of these steps in detail.

Step 1 – Designing the PCB Layout

The first step is to design the schematic and PCB layout for the board you want to etch using EDA (electronic design automation) software.

Creating the Schematic

• Draw the schematic diagram representing the electrical connections between components.
• Use part symbols to represent real-world component footprints.
• Connect symbols with nets showing electrical connectivity.
• Add power, input/output connectors etc.
• Assign component names, values, reference designators.
• Verify the circuit logic and connectivity.

Converting to PCB Layout

• Import the schematic into the PCB layout editor.
• Place component footprints onto the board canvas.
• Route traces to connect pads following the schematic netlist.
• Design power and ground planes, silkscreen, markings.
• Assign board thickness, dielectric layers, finish.
• Set track widths, clearances based on manufacturing capabilities.

Finalizing the Layout

• Check design rules like electrical spacing, annular rings.
• Run design rule check and resolve any errors.
• Verify board dimensions match required copper blank size.
• Add fabrication notes, drills table, etc.
• Export Gerber and drill files for production.

For DIY etching, simpler software with limited features can be used. Online free tools like EasyEDA, KiCAD EDA etc. are good enough for simple designs.

Step 2 – Printing the Layout

The next step is to print the PCB layout onto a paper or directly onto the copper board. Here are two commonly used methods:

Toner Transfer

• Print layout onto glossy magazine paper using a laser printer.
• Use a high resolution 1200+ dpi printer for better print quality.
• Allow the ink to dry fully before transferring.
• Avoid using inkjet prints as ink will spread during transfer.

Direct PCB Inkjet Printing

• Use inkjet printer capable of printing on copper boards.
• Special inkjet inks are used which adhere to the copper surface.
• Allows greater precision without toner transfer issues.
• More expensive, but simpler process.

Toner transfer method is most commonly used for DIY etching. But direct inkjet PCB printers are getting more affordable and can provide better results.

Step 3 – Preparing the Copper Board

The copper board forms the raw PCB material onto which the etched traces will remain.

Selecting Copper Clad Boards

• Use single or double sided copper clad laminates.
• FR-4 glass epoxy is the most common and inexpensive option.
• Get boards with 1 oz (35 μm) or thicker copper foil.
• Match copper foil thickness to required PCB trace thickness.

Cutting the Board

• Cut the blank copper clad laminate to the required PCB dimensions using a hacksaw.
• Deburr the edges to prevent injury and board damage.
• Double check dimensions match the PCB layout.

Cleaning the Board

• Use fine grit sandpaper to scrub off any copper oxidation.
• Clean the board with isopropyl alcohol to remove oils and dust.
• Ensure blank copper surface is clean for printing/etching.

Step 4 – Transferring the Layout

This step transfers the PCB layout pattern from paper/printer onto the copper board.

Toner Transfer Method

• Place the paper print of the layout on the cleaned copper board.
• Use an iron set to a high cotton/linen setting to heat the paper.
• Press firmly and rub iron across the paper to fuse the toner onto copper.
• Let it cool, then soak paper in water to remove paper pulp.
• Gently scrub off remaining paper fibers from toner.

Inkjet Method

• No transfer required since layout is directly printed onto copper board.
• Place copper board into printer and select PCB printing mode.
• Check print quality and repeat if needed until toner/ink sticks cleanly.
• Let the ink fully dry as per printer instructions.

Step 5 – Etching the PCB Board

With the PCB layout applied on the board, the next step is to etch away the unwanted copper leaving only the desired traces.

Choosing an Etchant Solution

Common DIY etchant solutions include:

• Ferric Chloride – Most popular and fast acting etchant.
• Ammonium Persulfate – Slower but more controllable etch rate.
• Hydrogen Peroxide and Hydrochloric/Sulfuric Acid – More dangerous, faster etch.
• Vinegar and Hydrogen Peroxide – Slower etch rate but safe.

Etching the Board

• Fill a plastic tray with the chosen etchant solution.
• Immerse the PCB board completely in the liquid etchant.
• Agitate gently to expedite etching and allow fresh etchant contact.
• Periodically lift board and check progress of etching.
• When complete, wash off all solution under running water.

Etching Considerations

• Use adequate ventilation and eye/skin protection when handling etchant.
• Maintain proper solution strength and temperature for optimal etch rates.
• Agitate the solution and rotate board to speed up exposure of all surfaces.
• Dispose spent etchant properly based on environmental regulations.

Step 6 – Drilling Holes

PCBs require holes to mount electronic components and connectors.

PCB Drill Bit Sizes

Common hole sizes include:

• 0.8 mm – For IC and transistor leads
• 1 mm – For most through-hole component leads
• 1.5 mm – General purpose wiring holes
• 2 mm – For mounting connectors or thicker wires

Drilling Holes

• Use a small hobby drill with fine drill bits. Dremel tools work well.
• Print and stick the drill template on the board if available.
• Drill all holes marked on the template.
• Use a drill stand and eye protection while drilling.
• Remove any burrs around drilled holes with a larger bit.

Drilling Tips

• Secure board in a vise or clamp while drilling to prevent shifting.
• Start with a smaller pilot hole before using larger bit sizes.
• Apply light pressure and let the drill do the work.
• Frequently clear dust to prevent clogging drill flutes.
• Sharpen bits or replace when drill quality declines.

Step 7 – Finalizing the PCB

With etching and drilling complete, a few finishing steps complete the DIY PCB fabrication process.

Removing Ink/Toner

• Any remaining ink, toner, adhesive, tape on the PCB surface needs to be removed.
• Use acetone or paint thinner to scrub off ink and adhesive residue.

Cleaning Traces

• Remove any oxidation or coating formed on copper traces post-etching using fine sandpaper.
• Isopropyl alcohol wash also helps clean the traces.

Applying Solder Mask

• Brush on a DIY solder mask like clear nail polish to protect exposed copper traces.
• Avoid coating contact pads and drill holes.

Silkscreen and Markings

• Identify components and polarity with permanent marker ink.
• Or apply custom DIY silkscreen using toner transfer method.

Testing for Shorts/Opens

• Use a multimeter in continuity test mode to check for any unintended shorts between traces or open circuits.
• Probe test all tracks and drill holes to validate connectivity.

The PCB is now ready for soldering and assembling electronic components on it. Enjoy your DIY etched PCB!

Supplies Needed

Here are some of the common tools and materials needed for DIY PCB etching:

• Copper clad laminate sheets
• Laser printer and glossy paper
• Etchant solution and tray
• Small drill with bits
• Sandpaper, acetone, isopropyl, q-tips
• Transfer paper, magazine paper
• Coffee filters, plastic tongs
• Eye protection, nitrile gloves
• Multimeter for testing

Tips for Successful Etching

Follow these tips to help improve your DIY PCB etching outcomes:

• Use a toner transfer method for better precision over hand drawing traces.
• Select an optimal etchant and maintain correct temperature/strength.
• Agitate constantly and rinse board frequently during etching.
• Clamp board properly and take care while drilling to avoid drill skips.
• Clean off any residue after etching using solvents like acetone.
• Apply DIY solder mask and silkscreen for a professional finish.
• Work in a well ventilated area and exercise safety precautions at all times.

Common Issues and Solutions

Some common issues faced during DIY PCB etching and how to resolve them:

Problem: Etched traces have gaps or are partially eaten away.

Solution: Insufficient etching. Increase etchant concentration or etch longer.

Problem: Traces are over-etched and very thin.

Solution: Too much etching. Reduce etchant concentration or etch duration.

Problem: Holes are not centered or drill skips around.

Solution: Secure board better while drilling and apply less pressure.

Problem: Short circuits detected during testing.

Solution: Clean board properly to remove etchant residues causing shorts.

Problem: Excessive undercut and outline etching of traces

Solution: Reduce etching temperature and agitation to slow down etch rate.

Frequently Asked Questions

What resolution do I need for a DIY PCB printer?

For DIY etching, a printer resolution of 1200 DPI or higher is recommended. Laser printers typically provide 600+ dpi resolution. Specialized PCB inkjet printers offer up to 2400 dpi prints. Higher resolution allows greater precision with small trace designs.

Can I use a cloth iron for toner transfer?

Yes, a regular household iron can work for toner transfer. Use the highest cotton or linen setting. Apply firm pressure in circular motions for 5+ minutes for complete transfer. However, a special PCB laminator with adjustable temperature gives better results.

How do I know when the PCB etching is complete?

Check progress every 5-10 minutes after immersing the board in etchant. Lift out and inspect if all unwanted copper is etched away leaving only the printed toner/ink traces. Repeat etching if any copper remains between tracks.

What is the best drill bit size for PCBs?

For most through-hole components, a 1mm drill bit is ideal. For ICs, use a smaller 0.8mm size. For power components or connectors, 1.5mm or larger bits are required. Have multiple bit sizes handy for drilling different hole types.

Can I use a Dremel tool to drill PCB holes at home?

Yes, a Dremel rotary tool with fine drill bits is perfectly suitable for DIY PCB hole drilling. Secure the board properly and use gentle pressure. Change bits frequently for smooth hole drilling.