etching

90 Articles

Scanning electron micrograph of a microfabricated lens array

Getting A Fly’s-Eye View With Microfabricated Lens Arrays

September 7, 2021 by 11 Comments

Atomic force microscopy, laser ablation, and etching with a witches brew of toxic chemicals: sounds like [Zachary Tong] has been playing in the lab again, and this time he found a way to fabricate arrays of microscopic lenses as a result.

Like many of the best projects, [Zach]’s journey into micro-fabrication started with a happy accident. It happened while he was working on metal-activated chemical etching (MACE), which uses a noble metal catalyst to selectively carve high-aspect-ratio features in silicon. After blasting at a silver-coated silicon wafer with a laser, he noticed the ablation pits were very smooth and uniform after etching. This led him to several hypotheses about what was going on, all of which he was able to test.

The experiments themselves are pretty interesting, but what’s really cool is that [Zach] realized the smooth hemispherical pits in the silicon could act as a mold for an array of microscopic convex lenses. He was able to deposit a small amount of clear silicone resin into the mold by spin-coating, and (eventually) transfer the microlens array to a glass slide. The lenses are impressively small — hundreds of them over only a couple hundred square microns — and pretty well-formed. There’s always room for improvement, of course, but for an initial attempt based on a serendipitous finding, we’d call it a win. As for what good these lenses are, your guess is as good as ours. But novel processes like these tend to find a way to be useful, and the fact that this is coming out of a home lab doesn’t change that fact.

We find this kind of micro-fabrication fascinating. Whether it’s making OLED displays, micro-machining glass with plasma, or even rolling your own semiconductors, we can’t get enough of this stuff.

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Garage Semiconductor Fab Gets Reactive-Ion Etching Upgrade

June 29, 2021 by 21 Comments

It’s a problem that few of us will likely ever face: once you’ve built your first homemade integrated circuit, what do you do next? If you’re [Sam Zeloof], the answer is clear: build better integrated circuits.

At least that’s [Sam]’s plan, which his new reactive-ion etching setup aims to make possible. While his Z1 dual differential amplifier chip was a huge success, the photolithography process he used to create the chip had its limitations. The chemical etching process he used is a bit fussy, and prone to undercutting of the mask if the etchant seeps underneath it. As its name implies, RIE uses a plasma of highly reactive ions to do the etching instead, resulting in finer details and opening the door to using more advanced materials.

[Sam]’s RIE rig looks like a plumber’s stainless steel nightmare, in the middle of which sits a vacuum chamber for the wafer to be etched. After evacuating the air, a small amount of fluorinated gas — either carbon tetrafluoride or the always entertaining sulfur hexafluoride — is added to the chamber. A high-voltage feedthrough provides the RF energy needed to create a plasma, which knocks fluorine ions out of the process gas. The negatively charged and extremely reactive fluorine ions are attracted to the wafer, where they attack and etch away the surfaces that aren’t protected by a photoresist layer.

It all sounds simple enough, but the video below reveals the complexity. There are a lot of details, like correctly measuring vacuum, avoiding electrocution, keeping the vacuum pump oil from exploding, and dealing with toxic waste products. Hats off to [Sam’s dad] for pitching in to safely pipe the exhaust gases through the garage door. This ties with [Huygens Optics]’s latest endeavor for the “coolest things to do with fluorine” award.

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A Vacuum Battery Made For Looks And Learning

June 5, 2021 by 34 Comments

Looks and RGB LEDs are usually not a priority in tool batteries, but [Oleg Pevtsov] decided the battery for his DIY vacuum cleaner needed to be different. In the process, he learned some lessons in chemical etching, plating, machining, casting, and electronics. See the video after the break for the build compilation.

The core of the battery is just five 18650 cells in a 3D-printed holder with a BMS, but the real magic is in the external components. The outer body is a brass tube with the logo etched through the 0.6 mm wall. Getting the etching right took a few tries and a lot of frustration, but he eventually found success with a solution of sulfuric acid and nitric acid in a magnetically stirred container. For etch resist he sprayed lacquer on the outside and filled the inside with silicone. The inside was then coated with clear epoxy by allowing it to cure while spinning. The final touches were nickel plating, then gold plating, and a high polish.

The silver-plated connector on one end consists of a machined copper tip and ring, epoxied together for isolation. The tip has a multi-start external thread, allowing the female side of the connector to securely connect with a single twist. A set of RGB LEDs were added to the core to light up the battery from the inside. We have to hope the vacuum this is supposed to attach to is equally impressive.

This being Hackaday, we see a lot of custom power banks for all the custom electronics. These range from a small power bank for on-the-go soldering to a heavy metal beast with a built-in inverter.

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JavaScript App Uses Advanced Math To Make PCBs Easier To Etch

May 19, 2021 by 28 Comments

We all remember the litany from various math classes we’ve taken, where frustration at a failure to understand a difficult concept bubbles over into the classic, “When am I ever going to need to know this in real life?” But as we all know, even the most esoteric mathematical concepts have applications in the real world, and failure to master them can come back to haunt you.

Take Voronoi diagrams, for example. While we don’t recall being exposed to these in any math class, it turns out that they can be quite useful in a seemingly unrelated area: converting PCB designs into easy-to-etch tessellated patterns. Voronoi diagrams are in effect a plane divided into different regions, or “cells”, each centered on a “seed” object. Each cell is the set of points that are closer to a particular seed than they are to any other seed. For PCBs the seeds can be represented by the traces; dividing the plane up into cells around those traces results in a tessellated pattern that’s easily etched.

To make this useful to PCB creators, [Craig Iannello] came up with a JavaScript application that takes an image of a PCB, tessellates the traces, and spits out G-code suitable for a laser engraver. A blank PCB covered with a layer of spray paint, the tessellated pattern is engraved into the paint, and the board is etched and drilled in the usual fashion. [Craig]’s program makes allowances for adding specific features to the board, like odd-shaped pads or traces that need specific routing.

This isn’t the first time we’ve seen Voronoi diagrams employed for PCB design, but the method looks so easy that we’d love to give it a try. It even looks as though it might work for CNC milling of boards too.

PCB Bath Comes From Russia With Love

February 6, 2021 by 19 Comments

[Ruvin Kub] likes magnets, a lot. Most of his projects feature some sort of magnet and his PC board agitation bath is no exception. You can see a video about the device, below. We’ll admit our Russian is pretty rusty, but if you ask YouTube nicely it will translate the Russian subtitles into whatever language you like.

One of the things we liked about the video was that he uses hydrogen peroxide, citric acid, and salt as an etchant. We’ve seen the same mix with vinegar or muriatic acid instead of citric acid. We aren’t sure what the actual  translation is about why he doesn’t like ferric chloride, but YouTube says, “she’s too gloomy for my light souls.”

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Laser Blasts Out High-Quality PCBs

January 11, 2021 by 53 Comments

With how cheap and how fast custom PCBs have gotten, it almost doesn’t make sense to roll your own anymore, especially when you factor in the messy etching steps and the less than stellar results. That’s not the only way to create a PCB, of course, and if you happen to have access to a 20-Watt fiber laser, you can get some fantastic homemade PCBs that are hard to tell from commercial boards.

Lucikly, [Saulius Lukse] of Kurokesu fame has just such a laser on hand, and with a well-tuned toolchain and a few compromises, he’s able to turn out 0.1-mm pitch PCBs in 30 minutes. The compromises include single-sided boards and no through-holes, but that should still allow for a lot of different useful designs. The process starts with Gerbers going through FlatCAM and then getting imported into EZCAD for the laser. There’s a fair bit of manual tweaking before the laser starts burning away the copper between the traces, which took about 20 passes for 0.035-mm foil on FR4. We have to admit that watching the cutting proceed in the video below is pretty cool.

Once the traces are cut, UV-curable solder resist is applied to the whole board. After curing, the board goes back to the laser for another pass to expose the pads. A final few passes with the laser turned up to 11 cuts the finished board free. We wonder why the laser isn’t used to drill holes; we understand that vias would be hard to connect to the other side, but it seems like through-hole components could be supported. Maybe that’s where [Saulius] is headed with this eventually, since there are traces that terminate in what appears to be via pads.

Whatever the goal, these boards are really slick. We usually see lasers used to remove resist prior to traditional etching, so this is a nice change.

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Micromachining Glass With A Laser — Very, Very Slowly

January 9, 2021 by 28 Comments

When it comes to machining, the material that springs to mind is likely to be aluminum, steel, or plastic. We don’t necessarily think of glass as a material suitable for machining, at least not in the chuck-it-up-in-the-lathe sense. But glass is a material that needs to be shaped, too, and there are a bunch of different ways to accomplish that. Few, though, are as interesting as micromachining glass with laser-induced plasma bubbles. (Video, embedded below.)

The video below is from [Zachary Tong]. It runs a bit on the longish side, but we found it just chock full of information. The process, formally known as “laser-induced backside wet-etching,” uses a laser to blast away at a tank of copper sulfate. When a piece of glass is suspended on the surface of the solution and the laser is focused through the glass from the top, some interesting things happen.

The first pulse of the laser vaporizes the solution and decomposes the copper sulfate. Copper adsorbs onto the glass surface inside the protective vapor bubble, which lasts long enough for a second laser pulse to come along. That pulse heats up the adsorbed copper and the vapor in the original bubble, enough to melt a tiny bit of the glass. As the process is repeated, small features are slowly etched into the underside of the glass. [Zachary] demonstrates all this in the video, as well as what can go wrong when the settings are a bit off. There’s also some great high-speed footage of the process that’s worth the price of admission alone.

We doubt this process will be a mainstream method anytime soon, not least because it requires a 50-Watt Nd:YAG fiber laser. But it’s an interesting process that reminds us of [Zachary]’s other laser explorations, like using a laser and Kapton to make graphene supercapacitors.

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