If you’re making your own boards with SMD parts, you might want to get a solder paste stencil. Usually made of laser-cut mylar or extremely thin steel, these stencils allow you to squeegee solder paste onto your board’s pads and make assembly a whole lot easier. [Rochey] needed a stencil for a board he was working on, and lacking a laser cutter he turned to what he had available – a few bits of plastic and a CNC machine.
[Rochey] began making his stencils out of laminating pouches and an xacto knife. This worked well, but it was time-consuming, and a bit fiddly when cutting 1 mm square holes. To speed up the process, [Rochey] put one of these laminating pouches on his CNC machine, exported the ‘Top Cream’ layer in Eagle to the CNC software of his choice, and had his machine attack the plastic with a 1 mm drill bit.
To [Rochey]’s surprise, everything went as planned; in five minutes, he had a stencil with perfectly accurate holes that masked off everything but the SMD pads.
Thanks [Fabien] for sending this one in.
I wonder if the same technique can be used to 3d print a thin layer of ABS to use as a stencil.
Easy if you have a CNC…
For those of us who CNC mill PCBs this sounds perfect.
I read pencils :S
As did I. scrolling to fast I guess.
I wonder if a CriCut would work for that, sometimes I see a used/return on sale at a hobby store.
I have a Silhouette Cameo Vinyl cutter. I’m wondering if there is a material that can be cut by a hobby grade vinyl cutter for use as a stencil. Anyone have any experience trying this?
Take a look at this page on the Silhouette Cameo Cutter and solder paste stencils. I want one!!!
This doesn’t really help for thin pitch components, which mainly are a problem.
I use a paste dispenser and for any medium to large pad it works perfectly and is fast to use, only very thin pitch ICs are a problem.
i usually shrink the b/tCream layers before cnc’ing the stencils otherwise they’re too big. adjust the mask in the drc, change the min/max of the cream which i then mill out from 3 or 5 mil brass sheets that can be picked up from ace hardware etc.
have no problems with small pitch ic’s.
now we have a laser i’ve been doing them out of safe to burn plastic sheets, but the brass sheets are much hardier.
No, this is actually a pretty decent way to approach the problem. I do laser stencils at TechShop but even there it can be tough to size the cutouts correctly on fine pitch components.
The OP is just drilling one large hole in the center of each pad location, but you can get PCB drills in much smaller sizes. Create a script to line up some 0.5mm drills along an IC pad, and it’ll probably work quite well. It’s much easier to drill rather than route, and this would probably work on thin stainless or brass too.
I’m unsure that multiple drill “strikes” to make a single pad cutout is going to work that well (if that’s what you were suggesting). One of the major concerns with stenciling paste is getting a good release. Having little “cut-ins” in your cutout is likely going to prevent getting good paste release when lifting the stencil.
I single drill strike of the appropriate diameter seems (to me) like it would work better. Let the heat and the flux do its spoogy magic and flow over the remainder of the pad surface.