PCB Etching Machine And How to Make One

What is a PCB Etching Machine?

A PCB (printed circuit board) etching machine is a device used to chemically remove unwanted copper from a PCB, leaving behind the desired copper traces that form the actual circuit. PCB etching is a key step in the PCB fabrication process.

There are a few different methods used for PCB etching:
| Method | Description |
|—|—|
| Ferric Chloride | The most common chemical used. An acidic solution of ferric chloride is used to dissolve the unwanted copper. |
| Cupric Chloride | Similar to ferric chloride but uses a cupric chloride solution instead. Less common. |
| Ammonium Persulfate | An alternative to the chloride-based etchants. Mixed as a powder with water.|
| Acid Etching | Uses strong acids like hydrochloric or nitric acid. Hazardous and not recommended for DIY. |

Commercially made PCB etching machines are available and are very useful for quickly and consistently etching PCBs in volume. However, they can be quite expensive. Luckily, it’s possible to make your own DIY PCB etching machine with some fairly basic materials and a little know-how. Let’s go through how you can build your own PCB Etcher.

Materials Needed to Make a PCB Etching Machine

To construct a simple DIY PCB etching machine, you will need:

• A plastic or glass container that your PCB can lay flat in
• An aquarium air pump
• Aquarium tubing and an air stone
• Ferric chloride etching solution
• A way to heat the solution (aquarium heater, crock pot, etc) (optional but very helpful)

The size of your container will limit the maximum size of the PCBs you can etch. It’s good to use one a bit bigger than the largest board you anticipate making. You’ll also want one with a lid to contain fumes.

The aquarium air stone and pump serve to oxygenate and agitate the etching solution, which greatly speeds up the etching process. This is the key part that turns a simple tray of etchant into an “etching machine.”

Optionally heating the etchant to about 50°C/120°F will make the etching process work even faster, but it’s not strictly necessary, especially for smaller boards. An adjustable aquarium heater or a temperature-controlled crock pot (with the probe in the etchant) work well for this.

Of course, you’ll also need a prepared PCB with an etch resist applied to the traces you want to keep. This can be a professionally made mask or a hand-drawn one using an etch-resist pen.

Safety Precautions

Before we go into the construction details, a word about safety:

Ferric chloride and other etching solutions are harsh chemicals. Always wear gloves, eye protection, and work in a well-ventilated area when handling them. Avoid breathing the fumes. Clean up any spills immediately and dispose of used etchant properly (many localities have special disposal procedures for chemicals like these).

Heated etching solutions are even more hazardous. Use caution and keep the temperature no higher than necessary to avoid boiling or splattering.

Constructing the Etching Machine

Now, let’s put it all together:

1. Drill a hole in the lid of your container for the air tubing. It should be a snug fit to avoid etchant splashing out.

2. Cut a length of aquarium tubing long enough to go from your air pump to the inside of the container, with a bit of slack.

3. Attach the air stone to one end of the tubing and feed the other end through the hole in the lid.

4. Place the air stone in the bottom center of the container.

5. Fill the container with enough ferric chloride solution to cover your PCB by about half an inch. The exact amount will depend on the size of your container and PCB.

6. If using a heater, set it up now according to its instructions. Aim for a temperature of around 50°C/120°F.

7. Connect the free end of the air tubing to your air pump.

That’s it! Your etching machine is ready to go.

Using the Etching Machine

To etch a PCB:

1. Carefully place your prepared PCB into the etchant solution, copper side up.

2. Put the lid on the container.

3. Turn on the air pump (and heater, if using).

4. Monitor the etching process. The time required will vary based on the strength and temperature of the etchant, but it typically takes anywhere from 5-30 minutes.

5. Periodically check the PCB. When all the unwanted copper has been removed, the etching is complete.

6. Turn off the pump and heater. Use tongs or gloved hands to remove the PCB.

7. Rinse the etched PCB thoroughly with water. The etch resist can then be removed with acetone (for professionally made masks) or abrasively for hand-drawn ones.

Your PCB is now ready for drilling and soldering of components!

After use, the etchant can be stored in the container for future use. It will eventually become exhausted and need to be replaced, but can typically be used for quite a few boards before that happens.

Tips for Optimal Etching

Here are a few tips to get the best results from your DIY PCB etching machine:

• Keep your etchant fresh. As it gets used, it will start to get saturated with copper and etch more slowly. Replace it when this starts to happen.

• Don’t skimp on the air pump. Good oxygenation and agitation of the etchant is key to fast, even etching.

• Heating the etchant will significantly speed up etching, especially for larger boards. Just be cautious and don’t let it get too hot.

• Double-check your etch resist before etching. Any gaps or thin spots will result in broken traces.

• If etching is uneven, your air stone placement may need adjustment, or your PCB may not be lying flat.

• Clean your PCB thoroughly after etching. Any residual etchant can corrode the copper over time.

With practice and experimentation, you’ll be able to dial in the perfect process for your needs.

Advantages of Using a PCB Etching Machine

So why go to the trouble of building a PCB etching machine? Here are a few key advantages:

If you’re getting serious about making your own PCBs, an etching machine is a great addition to your workshop.

Frequently Asked Questions

1. Q: Can I use a different chemical for etching besides ferric chloride?
   A: Yes, cupric chloride and ammonium persulfate are also commonly used. Each has its pros and cons in terms of speed, disposal, and safety. Ferric chloride is the most popular choice for DIY use.

2. Q: How long does the etchant last?
   A: It depends on the volume of etchant and how much copper it has to dissolve. Typically, you can etch quite a few boards before it needs to be replaced. You’ll know it’s time when etching starts to slow down significantly.

3. Q: Is it necessary to heat the etchant?
   A: No, it’s not necessary, but it will make etching much faster, particularly for larger boards. Room temperature etching will work, it will just take longer.

4. Q: What’s the best way to dispose of used etchant?
   A: This can vary by locality. Many areas have designated disposal sites for hazardous household chemicals. Contact your local waste management authority for guidance. Never pour it down the drain.

5. Q: Can I make double-sided PCBs with this method?
   A: Yes! You’ll need to apply etch resist to both sides and ensure that the PCB is suspended in the middle of the etchant bath so both sides etch evenly. You may need to flip it over halfway through etching.

Conclusion

Building your own PCB etching machine is a fairly simple and very useful project for anyone regularly making their own PCBs. With just a few basic components and some readily available chemicals, you can dramatically speed up your PCB fabrication process.

Always prioritize safety when working with etchants, and dispose of them properly. With a bit of practice, your DIY etching machine can produce PCBs every bit as good as commercially made ones. Happy etching!