Electrical engineers and technicians often use breadboards for prototyping and testing circuit designs. Breadboards are typically plastic plates with grids of spring-loaded receiving holes for inserting wires and components. While breadboards are great for quickly mocking up circuit layouts, they have several drawbacks. They are large, so they easily don’t fit into mechanical housings. They can get cluttered, which makes it difficult to chase down defects on complex layouts. Since they are not soldered, they are also not very robust.
For these reasons, designers are often eager to have Printed Circuit Boards (PCBs) manufactured as early in the design process as possible. A PCB is a flat board with conductive lines called traces on its surface for electrically connecting electronic parts and components.
Unfortunately, between tooling costs, high prices for low quantities, slow turnaround times and limits in redesign flexibility, a small manufacturing run for a PCB can be prohibitive. As a result, some designers have turned to milling their own PCBs using in-house, engraving CNC machines.
In order to mill a PCB, a wiring diagram must first be translated into a CAD model.
Since CAD modeling is an important step in product design, creating models early is an excellent habit for product development. Next, these models need to be translated to the CNC programming language G-code with a CAD/CAM translation software. Once the G-code is generated, you are ready to mill a circuit board.
There are a few things to keep in mind when milling PCBs.
- Drill, Mill, Cut: There are three processes for creating a PCB. First vias (holes for components) are drilled. Second, the clearances for the traces are milled. Finally, the board is cut to shape.
- Tooling: Each process should use the appropriate tools. Drills for holes; endmills, either square or v-tipped, for trace clearances; and endmills for shaping.
- Machine Performance: There are a variety of small CNC machines on the market with significant differences in built quality. Some are preassembled, while others require assembly on-site. The stiffness and build quality of the machine will dictate how accurately and precisely it mills. A lower-quality machine does not necessarily mean it can’t be used for prototyping PCBs, it just means you may need to account for larger trace clearances, use deeper cuts or use larger tooling.
- PCB Materials: Circuit boards consist of a copper layer bonded to a composite substrate that is often made of a flame-retardant material. FR-4 is one of the most popular substrates in use today. It is a glass-filed, epoxy resin. That glass fill makes the material highly abrasive, which will result in fast tool wear. Precautions should also be taken to avoid inhaling FR-4 dust, which is hazardous to one’s health.
- Finishing: The copper layer is prone to oxidization, which can diminish its electrical performance. So, once your PCB is milled and the components are soldered in place, it is important to coat the copper. Luckily, a quick coat of nail polish can address this issue.
Interested in milling your own PCBs with a CNC machine? Give us a call or contact us online to find the machine that’s right for you today!