Stencil Vacuum-Assist Helps Avoid The Heartbreak Of Smeared Solder Paste

December 22, 2021 by Dan Maloney 9 Comments

While using a stencil should make solder paste application onto PCBs a simple affair, there are a number of “gotchas” that make it more art than science. Luckily, there are tools you can build, like this 3D-printed vacuum-assist stencil jig, that take a little of the finesse out of the process.

For those who haven’t had the pleasure, solder paste stencils are often used to make the job of applying just the right amount of solder paste onto the pads of a PCB, and only on the pads. The problem is that once the solder paste has been squeegeed through the holes in the stencil, it’s not easy to remove the stencil without smearing. [Marius Heier]’s stencil box is essentially a chamber that attaches to a shop vac, along with a two-piece perforated work surface. The center part of the top platform is fixed, while the outer section moves up and down on 3D-printed springs.

In use, the PCB is placed on the center fixed platform, while the stencil sits atop it. Suction pulls the stencil firmly down onto the PCB and holds it there while the solder paste is applied. Releasing the suction causes the outer section of the platform to spring up vertically, resulting in nice, neat solder-covered pads. [Marius] demonstrates the box in the video below, and shows a number of adapters that would make it work with different sized PCBs.

If you think you’ve seen a manual vacuum stencil box around here recently, you’re right — we featured one by [UnexpectedMaker] not too long ago.

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Streamline Your SMD Assembly Process With 3D-Printed Jigs

November 9, 2021 by Adam Zeloof 12 Comments

Your brand-new PCBs just showed up, and this time you even remembered to order a stencil. You lay the stencil on one of the boards, hold it down with one hand, and use the other to wipe some solder paste across…. and the stencil shifts, making a mess and smearing paste across the board. Wash, rinse (with some IPA, of course), repeat, and hope it’ll work better on the next try.

openscad window — A PCB jig generated by OpenSCAD

Maybe it’s time to try Stencilframer, a 3D-printable jig generator created by [Igor]. This incredibly useful tool takes either a set of gerbers or a KiCad PCB file and generates 3D models of a jig and a frame to securely hold the board and associated stencil. The tool itself is a Python script that uses OpenSCAD for all 3D geometry generation. From there, it’s a simple matter to throw the jig and frame models on a 3D printer and voilà!– perfectly-aligned stencils, every time.

This is a seriously brilliant script. Anyone whose gone through the frustration of trying to align a stencil by hand should be jumping at the opportunity to try this out on their next build. It could even be paired with an Open Reflow hot plate for a fully open-source PCB assembly workflow.

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CNC Scroll Saw Add-On Cuts Beautiful Wooden Spirals

March 25, 2021 by Dan Maloney 23 Comments

If there’s one thing that woodworkers have always been good at, it’s coming up with clever jigs and work-holding solutions. Most jigs, however, are considerably simpler and more static than this CNC-controlled scroll saw add-on that makes cool wooden spirals a snap.

As interesting as the products of this setup are, what we like about this is the obvious care and craftsmanship [rschoenm] put into making what amounts to a hybrid between a scroll saw and a lathe. Scroll saws are normally used to make narrow-kerf cuts in thin, delicate materials, often with complicated designs using very tight radius turns. In this case, though, stock is held between centers on the lathe-like carriage. The jig uses a linear slide driven by a stepper and a lead screw to translate the workpiece perpendicular to the scroll saw blade while a geared headstock rotates it. Starting with the blade inserted into a through-hole, the saw slowly cuts a beautiful nested spiral down the length of the workpiece. An Uno, a GRBL shield, and some stepper drivers let a little G-code control the two axes of the jig.

The video below shows it in action; things do get a bit wobbly as the cut progresses, but in general the jig works wonderfully and results in some lovely pieces. At first we thought these would purely be objets d’art, but then we thought about this compression screw grinder for DIY injection molding machines and realized these wooden screws look pretty similar.

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Denim Sunglasses Frames Use A Wicked Set Of Jigs

July 30, 2020 by Mike Szczys 11 Comments

An obligatory “Future’s so bright I gotta wear… denim” joke is the only way to kick off this article. Sorry!

Now that that’s out of the way, how would you turn your own blue jeans into sunglasses? Well you wouldn’t, unless you’ve built an intricate jig for assembling sunglasses frames like [Mosevic] has done. Boiled down, this is like making parts out of carbon fiber, except you swap in denim for the carbon fiber. Several layers of blue jean material are layered in a mold and impregnated with resin. Once hardened, parts can be milled or laser cut from this stock and then assembled into the frames all of the hipsters are after.

For us its the assembly jig that’s so interesting to see. [Mosevic] shared it in an unlisted video of an update to the Kickstarter campaign which ran at the end of 2019. The jig is used to align machined parts into stack ups that include brass reinforcement and pins to align layers, as well as the joining for the three parts of the frame via the metal hinges. Most of the jig is made from machined plywood. The plates that hold the three parts of the frame, the “frame front” and the two “temples” in eyeglass parlance, are interchangeable so that the same jig can be used to assemble several variants of the frame design. The most notable non-plywood part of the jig are two metal clamps that hold the hinge into the frame front as the glue dries, holding a couple of tiny chunks of denim/resin block in place.

Here you can see the jig with all clamps fully closed. There is not an insignificant amount of time just getting the parts into this jig. But parts still need quite a bit of cleanup after this process to sand, shape, and polish all edges and surfaces of the frames. And of course you have to figure in the time it took to make the parts that went into the jig in the first place. The finished frames are gorgeous, but we have a lot more respect having seen what it takes to pull it off.

Now if you like your glasses like George Washington liked his false teeth, here’s how you can pull a set of shades out of your woodshop.

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This Four-Axis Stencil Printer Is The Ultimate In SMD Alignment Tools

July 26, 2020 by Dan Maloney 7 Comments

Here at Hackaday we love all kinds of builds, and we celebrate anytime anyone puts parts together into something else. And while we love the quick and dirty builds, there’s just something about the fit and finish of this four-axis SMD stencil printer that really pushes our buttons.

This build comes to us from [Phillip], who like many surface-mount users was sick of the various tape-and-PCB methods that are commonly used to align the solder stencil with the PCB traces. His solution is this fully adjustable stencil holder made from aluminum extrusions joined by 3D-printed parts. The flip-up frame of the device has a pair of clamps for securely holding the stainless steel stencil. Springs on the clamp guide rods provide some preload to keep the stencil taut as well as protection from overtensioning.

The stencil can move in the X-, Y-, and Z-axes to line up with a PCB held with 3D-printed standoffs on a bed below the top frame. The bed itself rotates slightly to overcome any skew in alignment of the PCB. [Phillip] was aghast at the price of an off-the-shelf slew-ring bearing for that axis, but luckily was able to print up some parts and just use simple roller bearing to do the same thing for a fraction of the cost. The frame is shown in use below; the moment when the pads line up perfectly through the stencil holds is oddly satisfying.

This puts us in mind of a recent, similar stencil printer we covered. That one was far simpler, but either one of these beats the expedient alignment methods hands down.

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Adjustable Jig Eases PCB Stencil Alignment Process

June 7, 2020 by Dan Maloney 8 Comments

PCB stencils make application of solder paste a snap, but there’s a long, fussy way to go before the paste goes on. You’ve got to come up with some way to accurately align the stencil over the board, which more often than not involves a jury-rigged setup using tape and old PCBs, along with a fair amount of finesse and a dollop of luck.

Luckily, [Valera Perinski] has come up with a better way to deal with stencils. The Stencil Printer is a flexible, adjustable alignment jig that reduces the amount of tedious adjustment needed to get things just so. The jig is built mostly from aluminum extrusions and 3D-printed parts, along with a bunch of off-the-shelf hardware. The mechanism has a hinged frame that holds the stencil in a fixed position above a platen, upon which rests the target PCB. The board is held in place by clamps that ride on threaded rods; with the stencil flipped down over the board, the user can finely adjust the relative positions of the board and the stencil, resulting in perfect alignment. The video below is mainly a construction montage, but if you skip to about the 29:00 mark, you’ll see the jig put through its paces.

Granted, such a tool is a lot more work than tape and spare PCBs, but if you do a lot of SMD work, it may be worth the effort. It’s certainly less effort than a solder-paste dispensing robot.

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Building One Test Fixture To Rule Them All

May 31, 2020 by Donald Papp 3 Comments

Test and programming fixtures are great time-savers for anyone who needs to deal with more than a handful of PCBs. Instead of plugging in connectors (or awkwardly holding probe tips or wires) to program some firmware or run tests, one simply pops a PCB into a custom fixture with one hand, and sips a margarita with the other while a program decides whether everything is as it should be. Test fixtures tend to be custom-made for specific board layouts, meaning one tester is needed per board or device type, but this work is easily justified by the huge time savings they offer.

An inserted PCB sits atop the thick acrylic piece, with pogo pins making contact from below. Generous space on the left and right make sure there is clearance for any mounted components. Visible near the bottom of the green board are output LEDs, and two touch-sensitive pads.

But the fine folks at Sparkfun’s quality control department figured they could save even more time by exploiting common design features across different boards, and shared details about designing a single test fixture flexible enough to handle multiple board types and designs.

The test unit looks like pretty familiar stuff at first glance: some hardware responsible for running the test program, laser-cut acrylic jig to hold a test PCB in a consistent position, spring-loaded pogo pins to make temporary electrical connections, and LEDs to clearly indicate PASS and FAIL states. The clever part is the way the fixture is designed to accommodate multiple board designs, and how it uses several 74LVC4066 quad bilateral switch ICs to take care of switching which pogo pins are connected and to where.

As mentioned, to be compatible with multiple boards there must be common design elements to exploit. In Sparkfun’s case, the through-hole connections on their breakout boards are all in a row with standard 0.1″ spacing. By using the aforementioned pogo pins and 4066 ICs, different pinouts can be accommodated and multiple board types can be used without any need to swap to different test hardware.

Test and programming fixtures, being one-offs, tend to have a lot of space for creativity and often show clever design or re-purposing of parts. Our own [Bob Baddeley] explains all about them here.