Shenzhen Alu Rapid Prototype Precision Co., Ltd.

CNC PCB prototyping is the process of using a CNC milling machine (Computer Numerical Control) to directly fabricate printed circuit boards (PCBs) in small quantities, typically for prototypes or low-volume production, without needing traditional chemical etching.

How It Works

A CNC machine physically removes unwanted copper from a copper-clad board (usually FR4 or similar) to create the desired circuit traces and pads. It's a subtractive mechanical process instead of the chemical (subtractive with photoresist + etchant) or additive (like toner transfer) methods hobbyists often use.

Common steps in CNC PCB prototyping:

1.Design the PCB in software (KiCad, Eagle, Altium, Fusion 360, etc.).

2.Generate toolpaths using CAM software (e.g., FlatCAM, pcb2gcode, Fusion 360, CopperCAM, Carbide Create + mods, or dedicated tools like Bantam Tools software).

3.Mill the traces: An isolation routing tool (usually a V-shaped engraving bit, 0.1–0.2 mm tip) cuts narrow grooves around copper traces to electrically isolate them.Typical trace/space capability: 0.1 mm (4 mil) to 0.25 mm (10 mil) with good machines and sharp tools.

4.Drill holes for through-hole components or vias (using regular drill bits).

5.Cut out the board outline (contouring).

Two Main CNC Approaches

1.Mechanical etching/isolation milling (most common):

Removes copper around traces.

Leaves the copper traces raised.

2.Rubbing/engraving (less common):

Mills away everything except the traces (deeper cuts).

Pros of CNC PCB Prototyping

1.No messy chemicals (ferric chloride, etc.).

2.Very fast turnaround (minutes to hours).

3.Double-sided boards are easy (just flip the board and align carefully).

4.Can mill on almost any copper-clad substrate (FR4, aluminum-5.backed, flexible, etc.).

5.Excellent for RF/microwave boards (precise control over copper removal).

6.Can add engraving, solder mask removal, or even 3D features.

Cons / Limitations

1.Minimum trace width/spacing is limited by tool size and machine precision (rarely below 4–6 mil reliably in hobby setups).

2.Leaves rougher edges on traces compared to photo-etched boards.

3.V-bits wear out and need frequent replacement.

4.Alignment for double-sided boards can be tricky without good fixturing.

5.Not cost-effective for medium/large volumes (professional PCB fabs are cheaper above ~10–50 boards).

In short: CNC PCB prototyping is a quick, clean, in-house way to make professional-looking prototypes (especially double-sided or complex ones) using a small milling machine instead of chemicals. It’s extremely popular among makers, small companies, and R&D labs that need boards the same day.