DIY PCB Master Class Part 1: Why You Should Ditch the Acid for a CNC Mill

Introduction

Every electronics hobbyist knows the struggle. You’ve designed the perfect circuit in EasyEDA or KiCad. You are ready to build it. You send the files off to a budget fab house, pay for shipping, and wait.

Two weeks later, the package arrives. You excitedly solder up the first board, plug it in... and nothing happens. You realize you forgot a single pull-up resistor or crossed a trace. Now, you are weeks behind schedule with a stack of five useless green coasters on your desk.

There is a better way—one that sits right on your desktop and can turn a blank copper board into a finished, testable circuit in under an hour.

Welcome to Part 1 of our PCB Milling Master Class. In this series, we are going to take you from zero knowledge to producing double-sided, professional-quality circuit boards using a CNC router. Today, we start with the basics: Why you should be milling instead of etching or ordering out.

The Prototyping Advantage: Fail Fast, Succeed Sooner

Before we even talk about the machinery, we need to talk about the workflow.

In software development, there is a concept called "Rapid Prototyping." You write code, run it, see it crash, fix it, and run it again. CNC milling brings that same speed to hardware.

• If you order your boards online, your "iteration time" is 1-2 weeks. If you make a mistake, you lose weeks.
• If you mill your boards at home, your "iteration time" is 45 minutes.

The Ideal Workflow:

1. Design your board.
2. Mill a quick-and-dirty prototype on your CNC.
3. Solder it and test it.
4. Find the bugs. (There are always bugs).
5. Update your design file.
6. Now send the perfect file to the professional fab house for the final batch.

Milling at home isn't necessarily about replacing professional boards; it's about verifying your design so you don't waste money and time ordering bad ones.

The Showdown: Milling vs. Chemical Etching
For decades, the "Ferric Chloride" method was the gold standard for home DIY. You print a design using laser toner, iron it onto a board, and soak it in acid. While it works, it is fraught with issues that CNC milling solves completely.

The Cons of Chemical Etching:

• The Mess: You are dealing with permanent staining acids that you cannot pour down the drain. Disposal is a generic headache.
• The "Undercut": As the acid eats down into the copper, it also eats sideways. This creates ragged trace edges and makes fine-pitch components incredibly difficult to solder.
• Manual Drilling: This is the worst part. After you etch the board, you have to sit there with a Dremel and manually drill every single hole for your resistors and capacitors. It is tedious and rarely accurate.

The Pros of CNC Milling (Isolation Routing):

• Mechanical Precision: The machine uses a V-shaped bit to remove just the copper needed to isolate the trace. The lines are razor-sharp and perfectly straight.
• Drilling is Automatic: The machine cuts the traces and then automatically drills the holes. When you pull the board off the machine, it is ready to populate.
• Cleanliness: No liquids, no fumes, no stains. Just a little bit of dust to vacuum up.

Do You Need an Expensive Machine?

This is the biggest myth in PCB manufacturing. You do not need a $5,000 industrial mill to make circuit boards.

PCB milling involves removing a layer of copper that is only about 0.0014 inches (0.035mm) thick. The cutting forces required to do this are microscopic.

• The Entry Level (3018 CNC): The generic "3018" CNC routers found on Amazon are actually perfect for this. While they may struggle with aluminum or hardwoods, they cut copper clad boards like butter. With a few minor tweaks (which we will cover later in this series), a $200 machine can produce professional results.
• The Mid-Range: Machines like the Shapeoko, X-Carve, or Onefinity will handle this task with ease, though they are arguably overkill for just PCBs.

The Bottom Line: Don't let hardware envy stop you. If you have a machine that moves in X, Y, and Z, you can make PCBs.

Material Science: FR4 vs. FR1

When you order a board from a professional house, you get FR4. But for home milling, you need to make a choice.

1. FR4 (Fiberglass Reinforced Epoxy)

This is the industry standard green stuff. It is rigid, fire-resistant, and strong.

• The Problem: It is made of woven glass. When you mill it, you are creating microscopic glass dust. This is hazardous to breathe and incredibly abrasive, meaning it dulls your bits very fast.
• Verdict: Use only if you have excellent dust collection and safety gear.

2. FR1 (Phenolic Paper / Bakelite)

This is a composite paper material bonded with resin. It is usually a tan or brown color.

• The Benefit: It is much softer than fiberglass. Your bits will last 10x longer, and the dust—while still something you shouldn't snort—is not made of glass shards. It also mills cleaner, leaving fewer "fuzzy" edges on your traces.
• Verdict: We highly recommend FR1 for home milling. It is cheaper, safer, and easier on your tools.

Don't Troubleshoot Alone

Milling PCBs is a superpower, but it does have a learning curve. You will break bits, you will mess up your zero-height, and you will have questions about FlatCAM settings.

Don't go it alone.

What's Next?

You have your machine, you have your blank copper board, and you are ready to create. But how do you get that schematic from your computer to the CNC?

In Part 2 of the PCB Master Class, we are going to dive into the software. We will walk you through EasyEDA, explain why you need to design differently for milling than for etching, and show you how to export the Gerber files needed for the next step.

Stay tuned—time to turn that robot into a factory.