Rapid PCB Prototyping with VIA Grid: Laser Etching Pre-Fabricated Double-Sided Boards in 90 Minutes

Stephen Hawes

The Challenge of PCB Vias and the VIA Grid Solution [00:00:00]

Making vias (vertical interconnect access) for rapid PCB prototyping has traditionally been difficult and time-consuming, involving:

• Complex chemical processes like acid baths and electroplating

  

• Manual installation of large rivets that are not suitable for dense ICs

  

The VIA Grid concept proposes a solution:

• Using a standardized PCB blank with a pre-baked array of factory-made vias

  

  • This eliminates the need to create vias in a home setting, leveraging the efficiency of professional board shops
  • The user simply defines which vias are connected when etching traces on the front and back sides

    

• This method enables rapid prototyping, completing a functional double-sided PCB in under an hour for etching and under 90 minutes for the entire assembly process

  

The Rapid Prototyping Process [00:00:45]

The VIA Grid method streamlines PCB creation from design to functional board.

1. Design and Layout [00:00:45]

• Design the schematic as usual
• Drop the design into a VIA Grid template PCB in your EDA software (e.g., KiCad)
  • The template provides the locations of the pre-fabricated vias
  • Route the board normally, connecting to the available vias as needed

    

    

2. Laser Etching [00:00:59]

• Export the design and load it into LightBurn software
• Use a DPSS (Diode Pump Solid State) UV laser to etch the copper traces
  • Etch the front side, then the back side

    

  • This process takes under an hour to produce a double-sided PCB with factory vias

    

3. Assembly [00:01:07]

• Couple the etched PCB with:
  • A LumenPnP pick-and-place machine

    

  • A paste extruder for solder paste application

    

  • A reflow oven for soldering components

    

• The entire process, from design to a finished, functional double-sided board, can be completed in under 90 minutes

  

Advanced Laser Technology for PCB Etching [00:01:27]

Traditional fiber lasers have limitations for PCB etching.

• Fiber lasers make FR4 (standard PCB substrate) conductive when cutting, requiring the use of less common FR1 substrates

  

The solution involves using DPSS UV lasers:

• These lasers use UV light and do not burn materials, preventing FR4 from becoming conductive
• The Commarker Omni 1 is an example of a commercially available DPSS laser at a reasonable price point

  

  • A new enclosed version (Commarker Omni X) offers improved safety features like ventilation and interlocks
• Achieving precise etching requires extensive tuning of laser settings (power, speed, frequency)

  

  • A custom LightBurn project file with optimized settings and alignment features is provided to simplify future use

    

    

    

Precision Alignment System and Jig [00:03:01]

Accurate alignment of the PCB with the laser is crucial for VIA Grid.

• Initial attempts at software-based alignment were tedious and imprecise

• A key discovery was that the laser is nearly invisible on the ENIG plating but lights up brightly on the exposed FR4 substrate

  

• Alignment Features ("Pac-Man" features):

  • VIA Grid PCBs are designed with small "Pac-Man" shaped features in the corners, exposing a slim path of fiberglass

    

    

  • When LightBurn's "frame" function is used at low power, these features light up perfectly when the board is aligned and scaled correctly

    

• Custom Alignment Jig:

  • A two-plate jig was developed for consistent physical alignment
  • The bottom plate bolts to the laser base

    

  • The top plate holds the PCB using three dowel pins and two spring-loaded cams for consistent re-indexing

    

  • The top plate is attached with four loose thumb screws, allowing for minor adjustments until the corner "Pac-Man" features align perfectly, then tightened

    

    

Via Arrangement and Future Possibilities [00:04:27]

Optimizing the via layout on the VIA Grid was an iterative process.

• Initial designs used tiny, densely packed via clusters

  

  • This resulted in an excessive number of vias and made alignment significantly more difficult
• The improved design spaces out the vias considerably
  • This creates a more forgiving layout, ensuring connections even if alignment isn't absolutely perfect

    

  • The increased spacing did not negatively impact usability

    

4-Layer Board Concept [00:05:01]

• The presenter explored the potential for a 4-layer board using this method
• Inner layers would be dedicated to fixed nets like power or ground planes
  • Specific vias would connect to inner layer 1 (e.g., power) and others to inner layer 2 (e.g., ground)

    

• This allows for even power/ground distribution but requires etching to isolate unused vias
  • This will add some etching time, but it's not much for the benefit gained.

Real-World Application and Future Vision [00:05:30]

VIA Grid has already demonstrated significant impact.

• A complex feeder PCB (a component shipped in thousands) was redesigned using VIA Grid

  

  • Layout took only 20 minutes
  • A fully finished PCB was ready in a couple of hours

    

• The laser can also drill holes for through-hole components, such as barrel jacks, directly into the PCB

  

The speaker believes this heralds a new wave of hardware prototyping:

• Engineering companies could have dedicated workbenches for 90-minute PCB prototyping, similar to the widespread adoption of 3D printers

  

• The process can also include applying solder mask for more professional-looking boards.

  

• This requires design concessions, primarily board size and via placement, but otherwise offers true design freedom

  

• The project encourages community collaboration, with all files (LightBurn project, VIA Grid PCB design, design rules, KiCad template, jig design) available on GitHub

  

  

  

  

The speaker is seeking feedback and suggestions for a new name for the "VIA Grid" standard, noting its current name was chosen randomly and the via layout resembles a graham cracker.