Jig to support wobbly PCB during assembly - Page 1
Forum section: electronics / general

author: pastaclub
author_rank: Regular Contributor
timestamp: September 25, 2025, 10:44:52 am
content: I have a panel with small PCBs which is a bit wobbly. It slightly bends when components are placed. It also needs many support bolts during pasting.I read that people sometimes use jigs that go underneath a PCB during assembly to make it mode rigid. This sounds like a good approach. But my stencil printer uses tooling holes (not fiducials), so how would you make a jig that supports the PCB, doesn't make it higher, and still allows you to use the tooling holes? What would the jig itself sit on?

author: Simmed
author_rank: Frequent Contributor
timestamp: September 25, 2025, 11:06:40 am
content: picture?

author: sokoloff
author_rank: Super Contributor
timestamp: September 25, 2025, 11:46:36 am
content: Unless I'm misunderstanding something, it seems like you could get some cellulose lattice composite (meaning, a piece of wood) of a suitable thickness and drill holes in it to allow the stencil printer's tooling pegs to pass through and hold the board and for the overall thickness of the wood to support the board.

author: Psi
author_rank: Super Contributor
timestamp: September 25, 2025, 12:00:52 pm
content: For support jigs, i've seen them made out of solder paste stencil material. Exactly the same process as making a laser cut stencil which makes sense, the PCB fab already has that capability.It's only for pick-n-place where the board has nothing under it and would otherwise bend or bounce on pnp head impact.For paste application it's sitting on a hard flat surface so isn't needed.The cut stencil gets screwed down/attached to a plastic/FR4 plate. The stencil is laser cut with huge opening in areas that need population while holding down all the other areas. Works good for flex PCBs / rigid flex were you can hold down the flexible ribbon areas that dont have any parts to populate.Sometimes the plastic/FR4 plate is depth routed to create a recess where the pcb sits into. Or a 2nd laser cut stencil is used in-between the two to create the same effect.Usually the PCB fab house creates the support/hold trays if they think its needed for population.

author: jpanhalt
author_rank: Super Contributor
timestamp: September 25, 2025, 01:06:22 pm
content: My homemade stencil printer is made from a tooling plate. The picture shows how I hold a PCB. The stencil is taped at top. It can be raised vertically on the guide posts.Your clamps can be made from PCB scraps to match the thickness of the PCB you are applying paste to. Mine are made from 1/16" aluminum, which is close enough. The posts are made from shoulder screws. The type used is shown but is not used with the printer.

author: SMTech
author_rank: Frequent Contributor
timestamp: September 25, 2025, 01:26:01 pm
content: I think we need a picture of your equipment to understand what we are working with. Commerical machines have PCB support options as standard particularly printers.

author: Psi
author_rank: Super Contributor
timestamp: September 25, 2025, 11:52:41 pm
content: Here's what I mean about using a solder paste stencil to turn a flexible panel into something rigid for pnp

author: loki42
author_rank: Frequent Contributor
timestamp: September 26, 2025, 05:12:14 am
content: Google board support and you'll see lots of options. Vacuum board support is very useful too if your setup supports it. Usually custom board supports will be cnc machined from aluminum but we also use Granite as you can lap it very flat. You can get artificial stone that you can drill holes in. That's very common for dual sided boards.Board support is the least discussed and most important topic in assembly i think. You can also look at stuff like grid lok.https://smt.asmpt.com/en/products/process-support-products/pcb-support-solutions/has a good range of pictures. We also use the swishy ones from count on tools. They are called ezload and you just place a few of them around. We use them in the pick and place machines and custom tooling in the printer.

author: SMTech
author_rank: Frequent Contributor
timestamp: September 26, 2025, 10:01:44 am
content: Quote from: loki42 on September 26, 2025, 05:12:14 amThere are clear knockoffs of ezload easily available on aliexpress. There are also very manual quasi-equivalents of gridlok (I haven't tried them).Very flexible panels or flex pcbs are often held on fixtures machined from materials with names like Durastone which hold the PCB through the whole line. There are specialist tooling companies out there to do this for you, but in principle if you have the tools, you can do it yourself.

author: SMTech
author_rank: Frequent Contributor
timestamp: September 26, 2025, 10:45:01 am
content: Quote from: loki42 on September 26, 2025, 05:12:14 amIs that what is going on here? The stainless sheet is acting as a clamp and has to be applied post printing with screws, which seems like a slow and tedious process suggesting either this board is expensive or there's more to it. As it is a vacumm plate or adhesive would make far more sense given that base plate is clearly already extensively machined.

author: loki42
author_rank: Frequent Contributor
timestamp: September 26, 2025, 04:46:12 pm
content: I think you replied to the wrong message. In the DEK stuff it's not screwed on, the carrier from the other message looks annoying as as you say you need to look it in. It looks to me like the type of carrier used for wave soldering or selective so I guess it's fine if you're using it for both.