Test Jig - PCB aligning  - Page 1
Forum section: electronics / projects

author: hcglitte
author_rank: Regular Contributor
timestamp: February 20, 2018, 12:15:53 pm
content: Hi,I have tried to think about different ways to easily align the PCB DUT into the test jig fixture. I will build the jig from various stacks of PCB's.Lower PCB: Solder pogo pins.Middle PCB1: Holes for pogo pins to keep them aligned and vertical.Middle PCB2: Cutout which is slightly smaller than the DUT PCB which the DUT PCB will press against and rest on.Upper PCB: Cutout for DUT PCB to keep it aligned.The upper PCB could be a stack of 2 or 3 pcs of the same PCB. This way the DUT PCB can "fall" into the slot before it "meets" the test pogo pins.Then it can be pressed further down onto the pogo pins until it meets the "Middle PCB2".The DUT can be held down by a clamp (the normal ones used), or there could becutout slots in the absolute upper PCB(s) where some sliders (PCB material as well) could be used to keep the DUT PCB down.These sliders will be gliding upon the lower "Upper PCB". These Upper PCBs could all be the same with removable mouse bite slots where thesliders is to be positioned. Actually with some clever design, all Middle and Upper PCB's could be the same design with removable cutouts etc.Another solution to the Upper PCB approach could be to use alignment pins. I have some concerns about this.Due to friction and tight tolerance it could be cumbersome to press the PCB down when there are 4 alignment pins.I have also trouble finding alignment pins which can be screwed onto the jig boards.There are lots of dowel pins, but these must somehow be secured to the jig boards.I thought of one solution: I could use 4 (or more) robust pogo pins with conical tip as alignment pins:https://www.aliexpress.com/store/product/Free-Shipping-100pcs-lot-P156-B-33-85mm-spring-test-probes-pogo-pin/518673_1686189927.htmlThis tip is 2mm thick (thickest I could find). I could have 1.5mm holes on the DUT PCB. The conical tip would enter the holes when positioning the PCB,then it can be pressed down until it meets the test point pogo pins. I would think that the conical tip will center align into the holes...The tips themselves are actually a tiny bit wobbling. The solution for this is to let the tip itself enter the Middle PCB1.Any tips, comments?

author: dmills
author_rank: Super Contributor
timestamp: February 20, 2018, 01:00:45 pm
content: They make alignment pins for this!Usually you use two heights of alignment pin, a taller one placed around the board edges to roughly align the board and then one slightly taller then the pogo pins tapered to fit into a couple of the board mounting holes to do the precision alignment before the pogo pins make contact.See also "Dowel pin".Another approach is to 3D print a fixture complete with guides, more suitable for small boards, but it does work.

author: hcglitte
author_rank: Regular Contributor
timestamp: February 20, 2018, 01:45:57 pm
content: Do you know of any source for these alignment pins?I have searched for dowel pins as mentioned, but these do not have threading. Hence they cannot be secured on the PCB jig.Good idea to use pins rather than PCB material for edge alignment.It would be nice if there were dowel pins which had threading on its half part.How does the tapered/conical alignment pins work exactly? I understand they act as a resting support pin for the PCB when fully pressed down.If however the test pins touch the PCB before it is perfectly aligned (centered on the tapered tip) then the test pins could bend when pressed further down, and they won't hit the target perfectly as well.So I would assume these tapered test pins should have a spring in them: Perfect alignment, then down-press.

author: ZomBiE80
author_rank: Contributor
timestamp: February 21, 2018, 10:49:09 am
content: I hand filed couple alignment pins from brass, Just be inventive and use anything you got in hand.

author: IconicPCB
author_rank: Super Contributor
timestamp: February 21, 2018, 12:06:14 pm
content: search for striper plate