• 1
    Designing for Testability

    First things first: to test a PCBA, I need reliable electrical access. That means adding test points to the PCB during design. I use 2 mm diameter test points to match the small spring-loaded pogo pins (a.k.a. test needles) I have on hand.

    You decide whether to place the test point on the top or bottom side. Both has its limitations and advantages.

    For the LED PCB example it is only possible on the top side due to the aluminium PCB. And I will not be blinded ;)

  • 2
    Preparing the Laser Cutter Files

    I export the outline and copper layers from KiCad (take your EDA) as SVG files, which I then import into LightBurn, the software I use to control my laser cutter. These SVGs serve as the basis for creating the test jig’s cutouts and alignment holes.

  • 3
    Layering the Plywood Jig

    The jig is made from three layers of 4 mm plywood, stacked and aligned using M4 screws and nuts. Here's how I configure each layer, from top to bottom:

    • Top Layer: This layer has a cutout for the PCB outline. 

      • I intentionally leave an additional 0.1 mm margin around the board to avoid a tight fit, making it easier to insert and remove the PCB. 

      • I also added some space for the fingers to grab the PBC easily.

      • Engraved markings provide additional information for the connectors, build date and fixture name. Which I placed wrong or forgot.
      • You could also add a clamp mechanism to hold the PCB down. I just use a needed heatsink and rubber bands.

    • Middle Layer: This is the functional core of the jig. It includes:

      • Holes for the pogo pins to align with the test points.

      • Additional cutouts to provide clearance for components, since the PCBA is placed upside down in the jig. In my example only a cutout for the LED.
        You might not need cutouts when you place the test points on the bottom layer and you only have top side components.

      • Acts as base where the PBC could lay on. You coud also add some EVA foam, pins or similar to keep the PCB from touching the wood.

    • Bottom Layer: This layer provides clearance beneath the pogo pins, allowing access for soldering wires or connectors to the pins. I added some cutouts to bring the wires back up to the top layer where I use angled pinheaders to interface with the LED drivers.

      • You could also add some extra space for different types of connectors or a separate PCB that will interface with the DUT.