I need some information. I sometimes order stencils with my smt pc boards when I buy them from JLCPCB. 99.99% of the projects I find and submit the gerbers do not have registration targets. I talked one designer into including registration marks. Since I hand solder (or hot air) all of them I find it still very hard to register the stencil on the pc board. I tried to talk him into putting a through hole via (tiny) in the middle so I could see the registration marks and possibly use a sewing pin to get it in the right spot but we found that you can not put any hole in a registration mark. Can someone suggest how I can do that?
Also going back to the stencil, all of them are large (11x14" or so) and the board itself may be a postage stamp. I have yet to find a way to get the pc board in the right place or near the right place since the board gets placed from the bottom and you can not see the top of the stencil. I have seen something that looks like an old photography contact frame that gets used commercially and starts at $1300! Even if someone has one of these or access to one (I do not) how do you get the board into the position needed?
And indeed the prices of these are surprisingly high (Often over EUR 1000) but there are also some simpler versions for below EUR 200. Some time ago I decided that if I needed one, I would make it myself. I’ve got all the tools (Lathe, metal mill, etc) to make it. (I would make a “frameless” version. But if I’d start giving myself a salary for the hours it would become more expensive quickly. And that is a part of the cause. These things are not mass produced consumer articles, and they must be quite reliable, and that are two reasons that make them more expensive.
For the postiioning, these things usually have screws with vernier scales to make small adjustments. I guess that first you do a rough positioning (if you can see the sides of pads though the holes, you know the stencil is not centered properly) After that you can deposit paste on one PCB and then verify whether the location is OK, and make small adjustments. If it was too far off, you just wipe the paste and do it again.
When you’re still aligning, you can also apply paste to just a few small sections (for exaomple in the corners of the PCB) to test for alignment. Maybe there are more tricks.
Drill alignment holes in the stencil and board, 2. Place the stencil first, 3. Place the board on top of it, 4. Stick pins into the holes, 5. Secure the board to the stencil with tape, 6. Flip the whole thing over, 7. With the stencil facing up, 8. Check that the stencil holes are in the correct position, and if successful, 9. There’s a good chance the board will be placed where you want it.
JLC offers the option to trim your stencil to any size. This will also save you shipping cost.
In a pinch, you can also cut it yourself with scissors (once) or shears.
If you hold the stencil an inch above the board and get your face up close, it’s not hard to do rough alignment. I’ve never needed anything other than pads for alignment targets.
That is what I am trying to do (drill alignment holes). As I said, the pcb program puts registration marks in 2 or more corners. I need a small (pin/needle size_ hole in the center of that registration target so I can use a sewing pin to get the stencil registered correctly on the board. I did wish I could just tell JLCPCB or PCBWay to cut the stencil to the board size. That would make registration easy!
You can communicate with them. Years ago we did this, as far as I remember it required explicit back and forth communication and drawing the outline in the paste layer. It was either PCBWay or JLCPCB.
I CNC-Mill my PCB’s and use a 1mm-Pin Diameter for Location-Ref. I made a Footprint and it gets Drilled allowing me to use the Locating-Pin in my milling Jig’s. The Jig’s have Mirrored Pin/hole so I can flip the PCB and Mill the other side accurately.
I don’t need stencils but, if I needed one, a stencil would also have the Hole. Sewing-needle is just a smaller diameter Pin so, it’s easy to make a STEP model if needing a Graphic for the 3D-Viewer…
Very simple and any PCB-fab house can drill the hole (it’s no different than any other Hole or Terminal-Pin.
