“Ever since we entered the SMD prototyping phase, there has been many questions about making an effective test/programming setup as the size of our prototypes was getting smaller and smaller,” the team states. “There wasn’t much real estate left to place test LEDs or things like extra screw holes. We had heard about bed of nails but it seemed like a fancy industrial setup only accessible to large factories. After much experimentation, we decided that it was time to update our process and get into easily reproducible precision.”
That’s where pogo jigs came in. If you’re not familiar with pogo pins, to begin with, they’re basically little needles with springs in them, used to create connections between electronic circuit boards. They’re quite fragile, unfortunately, and bend easily when inserted into jigs.
“Oftentimes, the layout of pogo pins has to be regular, following a grid or straight lines on the PCB,” the designers continue. “We’d like to benefit from the size of pogo pins to free up design, and allow different arrangements for pogo pins. In addition, alignment between pins and PCBs is done either by hand or by screwing the boards together. Not very fast or repeatable.”
Manually soldering pogo pins is a tedious process in which it’s all too easy to make a mistake – especially as a PCB gets smaller. Mis-contacts and shorting components become more of a risk, and while placing the contact pads in a straight line makes things easier, it also greatly limits design freedom. Furthermore, if pogo pins aren’t inserted completely flat into the board, they can be unstable, causing shorts and even permanent damage.
To circumvent these shortcomings, the designers used a da Vinci 1.0 Pro to design and 3D print their own precision pogo jig.
“This mini architecture functions like a sandwich with the 3D printed structure in the middle with pogo pins inserted,” the designers explain.
“You don’t have to worry anymore about the placement of the pins, they don’t need to be spread evenly across the plane or aligned,” the designers state. “The support afforded by the 3D printed holder doesn’t constrain the placement of your test pads on your board.”
Tolerances were included so that the insertion of the pins did not have to be precise in order for them to all touch the target sufficiently, while the 3D printed holder still held them tightly enough so that they wouldn’t fall out or tilt when the jig was moved. You can read further details about the assembly of the jig in the blog entry itself, but the important part is that when the designers powered up the jig and tested the circuit board, everything worked – and the whole process was much easier than it would have been without 3D printing.
“Ultimately, we replaced manual work by design work,” the designers conclude. “That way we can make many jigs quickly, modify and share easily modules that are generic enough that anyone would be able to use them for their own jigs…We feel that methods brought by 3D modeling/printing are opening up Electronic design and engineering to interesting solutions. We can truly work cross-discipline: It’s an exciting time to make things. Some of the constraints of the PCB world (grid, 2D, screws…) are disappearing: That’s quite liberating. More freedom in our design is achieved by associating support functions and electronic functions while keeping them separate.This also means that we can use less, cheaper, recyclable material and fulfill the same tasks. All of this in just a few hours.”
Discuss in the Pogo Jig forum at 3DPB.com.