Acrylic Stencils Help with Component Placement for SMD Assembly

Surface mount is where the action is in the world of DIY PCBs, and deservedly so. SMDs are so much smaller than through-hole components, and fewer holes to drill make surface-mount PCBs easier to manufacture. Reflow soldering is even a snap now thanks to DIY ovens and solder stencils you can get when you order your boards.

So what’s the point of adding another stencil to the surface-mount process? These component placement stencils are [James Bowman]’s solution for speeding up assembly of boards in production runs too small to justify a pick and place robot. [James] finds that placing small components like discrete resistors and caps easy, but struggles with the placement of the larger components, like QFN packaged microcontrollers. Getting such packages lined up exactly is hard when the leads are underneath, and he found repositioning led to smeared solder paste. His acrylic stencils, which are laser-cut from SVGs derived directly from the Eagle files with a script he provides, sandwich the prepped board and let him just drop the big packages into their holes. The acrylic pops off after placement, leaving the components stuck to the solder paste and ready for their trip to the Easy Bake.

[James] claims it really speeds up hand placement in his biggish runs, and it’s a whole lot cheaper than a dedicated robot. But as slick as we think this idea is, a DIY pick and place is still really sweet.

Simple Mechanism Gives Support for SMT Assembly

With the fine work needed for surface-mount technology, most of the job entails overcoming the limits of the human body. Eyes more than a couple of decades old need help to see what’s going on, and fingers that are fine for manipulating relatively large objects need mechanical assistance to grasp tiny SMT components. But where it can really fall apart is when you get the shakes, those involuntary tiny muscle movements that we rarely notice in the real world, but wreak havoc as we try to place components on a PCB.

To fight the shakes, you can do one of two things: remove the human, or improve the human. Unable to justify a pick and place robot for the former, [Tom] opted to build a quick hand support for surface-mount work, and the results are impressive considering it’s built entirely of scrap. It’s just a three-piece arm with standard butt hinges for joints; mounted so the hinge pins are perpendicular to the work surface and fitted with a horizontal hand rest, it constrains movement to a plane above the PCB. A hole in the hand rest for a small vacuum tip allows [Tom] to pick up a part and place it on the board — he reports that the tackiness of the solder paste is enough to remove the SMD from the tip. The video below shows it in action with decent results, but we wonder if an acrylic hand rest might provide better visibility.

Not ready for your own pick and place? That’s understandable; not every shop needs that scale of production. But we think this is a great idea for making SMT approachable to a wider audience.

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Make A Better, Spring-Loaded SMT Tape Strip Holder

Every so often, a project is worth some extra work to see if the idea can go any further. [JohnSL] has been busy doing exactly that with his spring-loaded SMT tape holder project. Having done the original with 3D printing, he has been working on designing for injection molding. This isn’t a motorized feeder, it’s still a manual tool but it is an improvement over the usual workshop expedient method of just sticking segments of tape down to the desktop. Tape is fed into the holders from one end and spring tension holds the tape firm while a small slot allows the cover tape to be guided backward after peeling. As anyone who has used cut segments of tape to manually deal with SMT parts knows, small vibrations — like those that come from peeling off the clear cover — can cause the smaller components to jump around and out of their pockets, and any length of peeled cover gets awkward quickly.

The design allows for multiple holders to mount side-by-side.

In [JohnSL]’s design, all SMT tapes sit at an even height regardless of size or tape thickness. A central support pushes up from the bottom with tension coming from a spring pulling sideways; the central support is forced upward by cams and presses against the bottom surface of the tape. As a result, the SMT tape gets supported from below with even tension and the whole assembly maintains a narrow profile suitable for stacking multiple holders side by side. The CAD files are available online along with a McMaster-Carr part number for the specific spring he used.

After working out the kinks on 3D printed prototypes, [JohnSL] decided to see if it would be feasible to design an injection molded version and made a video outlining the process, embedded below.

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Improved Perfboard For Surface Mount Parts

Look through the last two decades of electronics project built on perfboard, and you’ll notice a trend. Perfboard is designed for through-hole parts, but ever more frequently, the parts we need are only available as surface mount devices. What does this mean for the future of all those protoboard, veroboard, and tagboard designs? It’s not good, but fortunately, there may be an answer. It’s perfboard designed for mounting SOICs, SOTs, and other surface mount devices.

Perfboard is an extremely simple concept. Most through-hole electronic components are built around 0.1″ or 2.54 mm spacing between pins. Yes, there are exceptions, but you can always bend the middle pin of a transistor and put it in a hole. SMT devices are different. You can’t really bend the pins, and the pin pitch is too small for the 0.1″ holes in traditional perfboard.

[electronic_eel] is changing that game up with his own design for perfboard. This perfboard has the traditional 0.1″ holes, but there are SMD pads sprinkled about between these holes. The result is being able to solder SOIC, SOT23-6, SOT23 and SOT363 devices directly to a board alongside 0603 and 0805 devices. Connect everything with a few beads of solder and you have a functional circuit made out of surface mount devices on something that’s still compatible with the old protoboard designs.

This isn’t the first time we’ve seen a new type of protoboard make it into production. A few years ago, Perf+, a bizarre ‘bus-based’ protoboard solution came onto the scene, although that wasn’t really designed for SMD parts. While [electronic_eel] doesn’t have any plans to sell his protoboard, the files are available, and you can easily design your own small piece of perfboard.

What Lies Within: SMT Inductor Teardown

Ever wonder what’s inside a surface-mount inductor? Wonder no more as you watch this SMT inductor teardown video.

“Teardown” isn’t really accurate here, at least by the standard of [electronupdate]’s other component teardowns, like his looks inside LED light bulbs and das blinkenlights. “Rubdown” is more like it here, because what starts out as a rather solid looking SMT component needs to be ground down bit by bit to reveal the inner ferrite and copper goodness. [electronupdate] embedded the R30 SMT inductor in epoxy and hand lapped the whole thing until the windings were visible. Of course, just peeking inside is never enough, so he set upon an analysis of the inductor’s innards. Using a little careful macro photography and some simple image analysis, he verified the component’s data sheet claims; as an aside, is anyone else surprised that a tiny SMT component can handle 30 amps?

Looking for more practical applications for decapping components? How about iPhone brain surgery?

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Tools of the Trade – Inspection

In the last episode, we put our circuit boards through the reflow process. Unfortunately, it’s not 100% accurate, and there are often problems that can occur that need to be detected and fixed. That’s what the inspection step is for. One could insert an inspection step after paste, after placement, and after reflow, but the first two are icing on the cake — the phase where most mistakes can be caught is after reflow.

There are a number of problems typical with a surface mount reflow process: Continue reading “Tools of the Trade – Inspection”

Tools of the Trade – Reflow

In our previous issues in this series on making circuit boards, we covered placing solder paste and placing components. Now it’s time to bake our cake!

There are a variety of methods for reflowing a circuit board, but they all rely on a single principle: heat up the solder paste (a mixture of flux and solder) until the flux burns off and the solder becomes liquid, and then cool it down. Accomplishing this once or twice is easy; once you’ve played with a hot plate you’ll swear off through hole. Scaling it up and doing it repeatedly with high yield is extremely challenging, though. Continue reading “Tools of the Trade – Reflow”