In the BIDC Electronics lab, we have two machines that can mill out custom circuit boards. However, there are several considerations to take into account that will make your life much easier.

Our machines

  • Accurate 637 PCB Mill
    • Subtractive manufacturing. It starts with a sheet of copper clad FR4 and removes enough copper to separate the traces
    • Minimum clearance and trace width 0.4 mm
    • Recommended clearance and trace width 0.5 mm or greater
    • Traces are made of copper.
  • Voltera V-One
    • Additive manufacturing. It starts with a sheet of FR4 and adds conductive ink where there should be traces.
    • Minimum clearance and trace width 0.2 mm
    • Recommended clearance and trace width 0.4 mm or greater
    • Requires a special type of solder. We keep it in stock, but it is harder to use than normal solder.
    • Traces are made of conducive ink and have a higher resistance than copper.

The machines have a very large amount of overlap in their capabilities. That being said, they each have their own strengths and weaknesses.

You should use the Voltera if:

  • Your design does not have a ground plane
  • Your design has a requirement for very small clearances.
  • Your design uses only surface mount components

You should use the Accurate if:

  • Your design has a large ground plane
  • Your design can accommodate large traces
  • You have through hole components
  • Your board needs to be a custom shape
  • You have many many different hole sizes (>5 or so)
  • You have very large holes (>1 mm)

Types of PCB designs

These are sorted roughly in order of the ease of manufacturing and assembly afterwards. If you can make changes to move your board up the list, you will have a much easier time. The machine that tends to have the easier time with the type of PCB is listed, but you can use the other machine, especially if there is a reason to (see the above lists).

  1. Single-sided board with surface mount (SMD) components only
    • Prefer Voltera
  2. Single sided board with through hole components
    • Prefer Accurate
    • Make sure your parts are on the *back* of the board. Otherwise you’ll need to solder them on the wrong side.
  3. Double sided board with SMD components only
    • No preference. Vias are quite annoying to add
  4. Double sided board with through hole components
    • Prefer Accurate
  5. Boards that violate our size constraints.
    • Not possible for us to make.
  6. 3+ layer boards
    • Not possible for us to make.

DRC Files

We are currently working on files that contain all the relevant DRC rules. Until those are ready, the most important ones are listed here:

Accurate

  • Minimum Trace Clearance: 0.4 mm
  • Recommended Trace Width: 0.4 mm or greater
  • Minimum Hole size: 0.2 mm
  • Via hole size: 0.7mm
    • See section for alternative via sizes
  • Via pad size: 0.9 mm

Voltera

  • Minimum Trace Clearance: 0.2 mm
  • Recommended Trace Clearance: 0.4 mm
  • Minimum Trace Width: 0.2 mm
  • Recommended Trace Width: 0.4 mm or greater
  • Minimum Hole size: 0.2 mm
  • Recommended minimum hole size: 0.7 mm
  • Maximum Hole size: 1.6 mm
  • Via hole size: 0.7mm
    • See section for alternative via sizes
  • Via pad size: 0.9 mm

Vias

Vias connect the top and bottom layers of a board. They are essential for designing any two sided circuit. However, they are rather finicky to install. The recommended way is to use a rivet to connect the top and bottom layers of the board. Smaller via sizes can be achieved by soldering a fine wire through the hole, but this is extremely time consuming. We do not recommend this method.

IMPORTANT NOTE: Through hole parts do not behave as vias (not without extra work). Add a separate via next to through hole parts.

Via rivets are available in the following sizes. (drill size shown here) Larger sizes tend to be easier to install at the cost of more board space. For all sizes, add 50% to the drill size to get the pad size.

  • 0.7 mm
  • 0.9 mm
  • 1.3 mm
  • 1.5 mm
  • 1.7 mm