acid

20 Articles

Big Chemistry: Hydrofluoric Acid

February 27, 2024 by 32 Comments

For all of the semiconductor industry’s legendary reputation for cleanliness, the actual processes that go into making chips use some of the nastiest stuff imaginable. Silicon oxide is comes from nothing but boring old sand, and once it’s turned into ultrapure crystals and sliced into wafers, it still doesn’t do much. Making it into working circuits requires dopants like phosphorous and boron to give the silicon the proper semiconductor properties. But even then, a doped wafer doesn’t do much until an insulating layer of silicon dioxide is added and the unwanted bits are etched away. That’s a tall order, though; silicon dioxide is notoriously tough stuff, largely unreactive and therefore resistant to most chemicals. Only one substance will do the job: hydrofluoric acid, or HFA.

HFA has a bad reputation, and deservedly so, notwithstanding its somewhat overwrought treatment by Hollywood. It’s corrosive to just about everything, it’s extremely toxic, and if enough of it gets on your skin it’ll kill you slowly and leave you in agony the entire time. But it’s also absolutely necessary to make everything from pharmaceuticals to cookware, and it takes some big chemistry to do it safely and cheaply.

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Copper Be Gone: The Chemistry Behind PCB Etching

August 31, 2023 by 33 Comments

For a lot of reasons, home etching of PCBs is somewhat of a dying art. The main reason is the rise of quick-turn PCB fabrication services, of course; when you can send your Gerbers off and receive back a box with a dozen or so professionally made PCBs for a couple of bucks, why would you want to mess with etching your own?

Convenience and cost aside, there are a ton of valid reasons to spin up your own boards, ranging from not having to wait for shipping to just wanting to control the process yourself. Whichever camp you’re in, though, it pays to know what’s going on when your plain copper-clad board, adorned with your precious artwork, slips into the etching tank and becomes a printed circuit board. What exactly is going on in there to remove the copper? And how does the etching method affect the final product? Let’s take a look at a few of the more popular etching methods to understand the chemistry behind your boards.

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Op-Amp Challenge: Measuring PH, No Code Required

June 8, 2023 by 2 Comments

When you see a project with a digital display these days, you’ll be forgiven for assuming that there’s some kind of microcontroller behind the scenes. And while that’s often the easiest way to get a project from idea to completion, it’s rarely the most interesting way.

This digital pH meter is a great example of that “no-code” design philosophy. According to [chris], the main use for this meter will be to measure soil pH in his garden, and the reason for eschewing a microcontroller was more or less for the challenge. And quite a challenge it was. Understanding the concept of pH isn’t always easy, and many a budding chemist has fallen victim to its perils. Actually measuring pH isn’t much easier, with the need to account for a lot of variables while measuring small voltages. Adding to the challenge was the fact that pretty much every skill on display here — from using KiCad to SMD soldering — was the first time [chris] had tackled them.

To amplify the voltage from the off-the-shelf pH probe, [chris] chose an LMV358A, a high-impedance FET-input version of the venerable LM358 op-amp, so as not to load down the probe. A negative temperature coefficient (NTC) resistor in the feedback path provides temperature compensation. He also designed a split power supply to provide positive and negative rails from a single 9-volt battery. The 3.5-digit LCD display is driven by an ICL7106 integrated A/D converter and BCD driver chip. Everything went into a nice-looking plastic enclosure that’s very suitable for a portable instrument.

As of this writing, the Op-Amp Challenge has officially wrapped, and there’s a slew of last-minute entries we need to go through. Check out the competition and stay tuned to find out who the judges pick for op-amp design glory!

2023 Hackaday.io Op Amp Challenge

Mining And Refining: Sulfur

September 28, 2022 by 23 Comments

When you think of the periodic table, some elements just have a vibe to them that’s completely unscientific, but nonetheless undeniable. Precious metals like gold and silver are obvious examples, associated as they always have been with the wealth of kings. Copper and iron are sturdy working-class metals, each worthy of having entire ages of human industry named after them, with silicon now forming the backbone of our current Information Age. Carbon builds up the chemistry of life itself and fuels almost all human endeavors, and none of us would get very far without oxygen.

But what about sulfur? Nobody seems to think much about poor sulfur, and when they do it tends to be derogatory. Sulfur puts the stink in rotten eggs, threatens us when it spews from the mouths of volcanoes, and can become a deadly threat when used to make gunpowder. Sulfur seems like something more associated with the noxious processes and bleak factories of the early Industrial Revolution, not a component of our modern, high-technology world.

And yet despite its malodorous and low-tech reputation, there are actually few industrial processes that don’t depend on massive amounts of sulfur in some way. Sulfur is a critical ingredient in processes that form the foundation of almost all industry, so its production is usually a matter of national and economic security, which is odd considering that nearly all the sulfur we use is recovered from the waste of other industrial processes.

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Acid-Damaged Game Boy Restored

January 17, 2022 by 11 Comments

The original Game Boy was the greatest selling handheld video game system of all time, only to be surpassed by one of its successors. It still retains the #2 position by a wide margin, but even so, they’re getting along in years now and finding one in perfect working condition might be harder than you think. What’s more likely is you find one that’s missing components, has a malfunctioning screen, or has had its electronics corroded by the battery acid from a decades-old set of AAs.

That latter situation is where [Taylor] found himself and decided on performing a full restoration on this classic. To get started, he removed all of the components from the damaged area so he could see the paths of the traces. After doing some cleaning of the damage and removing the solder mask, he used 30 gauge wire to bridge the damaged parts of the PCB before repopulating all of the parts back to their rightful locations. A few needed to be replaced, but in the end the Game Boy was restored to its former 90s glory.

This build is an excellent example of what can be done with a finely tipped soldering iron while also being a reminder not to leave AA batteries in any devices for extended periods of time. The AA battery was always a weak point for the original Game Boys, so if you decide you want to get rid of batteries of any kind you can build one that does just that.

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Tiny Tesla Valves Etched In Glass

June 20, 2021 by 8 Comments

While it’s in vogue right now to name fancy new technology after Tesla, the actual inventor had plenty of his own creations that would come to bear his namesake, including Tesla coils, Tesla oscillators, Tesla turbines and even the infamous Tesla tower. One of the lesser known inventions of his is the Tesla valve, a check valve that allows flow in one direction without any moving parts, and [Huygens Optics] shows us a method of etching tiny versions of these valves into glass.

The build starts out with a fairly lengthy warning, which is standard practice when working with hydroflouric acid. The acid is needed to actually perform the etching, but it’s much more complicated than a typical etch due to the small size of the Tesla valves. He starts by mixing a buffered oxide etch, a mix of the hydroflouric acid, ammonia, and hydrochloric acid, which gives a much more even etching than any single acid alone. Similar to etching PCBs, a protective mask is needed to ensure that the etch only occurs where it’s needed. For that there are several options, each with their own benefits and downsides, but in the end [Huygens Optics] ends up with one of the smallest Tesla valves ever produced.

In fact, the valves are so small that they can only be seen with the aid of a microscope. While viewing them under the microscope he was able to test with a small drop of water to confirm that they do work as intended. And, while the valves that he is creating in this build are designed to work on liquids, [Huygens Optics] notes that the reason for making them this small was to make tiny optical components which they are known for.

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Learn IC Decapping

October 21, 2020 by 15 Comments

Decapsulating ICs used to be an exotic technique. (I should know, I did that professionally for one of the big IC vendors back in the 1980s.) These days, more and more people are learning to take apart ICs for a variety of reasons. If you are interested in doing it yourself, [Juan Carlos Jimenez] has a post you should read about using acid to remove epoxy from ICs.

[Juan Carlos] used several different techniques with varying degrees of success. Keep in mind, that using nitric acid is generally pretty nasty. You need safety equipment and be sure to plan for bad things to happen. Have eyewash ready because once you splash acid in your eye, it is too late to get that together.

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