Blast Away The Flux — With Brake Cleaner?

December 26, 2024 by Dan Maloney 74 Comments

Can you use brake cleaner for flux removal on PCBs? According to [Half Burnt Toast], yes you can. But should you? Well, that’s another matter.

In our experience, flux removal seems to be far more difficult than it should be. We’ve seen plenty of examples of a tiny drop of isopropyl alcohol and a bit of light agitation with a cotton swab being more than enough to loosen up even the nastiest baked-on flux. If we do the same thing, all we get is a gummy mess embedded with cotton fibers smeared all over the board. We might be doing something wrong, or perhaps using the wrong flux, but every time we get those results, we have to admit toying with the idea of more extreme measures.

The LED bar graphs were not a fan of the brake cleaner.

[Toast] went there, busting out a fresh can of brake cleaner and hosing down some of the crustier examples in his collection. The heady dry-cleaner aroma of perchloroethylene was soon in the air, and the powerful solvent along with the high-pressure aerosol blast seemed to work wonders on flux. The board substrate, the resist layer, and the silkscreen all seemed unaffected by the solvent, and the components were left mostly intact; one LED bar graph display did a little melty, though.

So it works, but you might want to think twice about it. The chlorinated formula he used for these tests is pretty strong stuff, and isn’t even available in a lot of places. Ironically, the more environmentally friendly stuff seems like it would be even worse, loaded as it is with acetone and toluene. Whichever formula you choose, proceed with caution and use the appropriate PPE.

What even is flux, and what makes it so hard to clean? Making your own might provide some answers.

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Stop Silicone Cure Inhibition, No Fancy Or Expensive Products Required

October 30, 2022 by Donald Papp 16 Comments

Casting parts in silicone is great, and 3D printing in resin is fantastic for making clean shapes, so it’s natural for an enterprising hacker to want to put the two together: 3D print the mold, pour in the silicone, receive parts! But silicone’s curing process can be inhibited by impurities. What’s cure inhibition? It’s a gross mess as shown in the image above, that’s what it is. Sadly, SLA-printed resin molds are notorious for causing exactly that. What’s a hacker to do?

Firstly: there are tin-cure and platinum-cure silicones, and for the most part tin-cure silicone works just fine in resin-printed molds. Platinum-cure silicones have better properties, but are much more susceptible to cure inhibition. Most workarounds rely on adding some kind of barrier coating to molds, but [Jan Mrázek] has a cheap and scalable method of avoiding this issue that we haven’t seen before. Continue reading “Stop Silicone Cure Inhibition, No Fancy Or Expensive Products Required” →

Better 3D Printing Via Chemistry?

August 21, 2022 by Al Williams 8 Comments

If you have problems getting a 3D print to stick to the bed, you might consider using glue to — hopefully temporarily — attach the print to the bed. In addition, some plastics glue together well if you use a solvent. [Stefan] asks the question: What if you use solvent to glue each layer of a 3D print to the previous layer? The answer is in the video below.

If you know [Stefan], he is always meticulous, so the first test was with normal ABS parts. Then he used a solvent to glue two broken parts together to show how a single layer does with bonding. Then he moved toward trying the solvent for each layer.

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Keycap Shine? No, Shiny Keycaps

August 19, 2022 by Kristina Panos 34 Comments

No matter how often you wash your hands, ABS keycaps will eventually exhibit shine wherever you strike them the most. And that’s the problem right there: the shine might be okay if it were somehow uniform across the surface of the keycaps, but instead it just tends to make one feel seen. And since there’s really nothing you can do except to replace your keycaps (or start with PBT), you might as well embrace the shine, right?

Well, that’s how [mmalluck] feels, anyway. He recently experimented with using acetone vapors to refinish a set of keycaps from Drop, making them super-duper shiny in the process. Now, the operative word here is vapors, because straight acetone would acid-wash those ‘caps faster than you can say ‘bad idea jeans’.

So to that end, [mmalluck] poured acetone in a glass cake pan, used a piece of cardboard to separate the keycaps from the acetone, and covered it all with a glass cutting board. It doesn’t take very long to achieve a good result, and [mmalluck] says it’s better to err on the side of too-short instead of risking reaching the point of too-melted.

We wouldn’t have thought we’d react this way, but we think they’re pretty cool looking. That particular set seems just right for this process, which makes them look like new old-stock typewriter keys or something. Looks way better than the ultra-personalized shine of usage. What do you think? Let us know in the comments.

Via KBD #90

Scavenging CDs For Flexible Parts

August 1, 2022 by Bryan Cockfield 42 Comments

CDs are becoming largely obsolete now, thanks to the speed of the internet and the reliability and low costs of other storage media. To help keep all of this plastic out of the landfills, many have been attempting to find uses for these old discs. One of the more intriguing methods of reprurposing CDs was recently published in Nature, which details a process to harvest and produce flexible biosensors from them.

The process involves exposing the CD to acetone for 90 seconds to loosen the material, then transferring the reflective layer to a plastic tape. From there, various cutting tools can be used to create the correct pattern for the substrate of the biosensor. This has been shown to be a much more cost-effective method to produce this type of material when compared to modern production methods, and can also be performed with readily available parts and supplies as well.

The only downside to this method is that it was only tested out on CDs which used gold as the conducting layer. The much more common aluminum discs were not tested, but it could be possible with some additional research. So, if you have a bunch of CD-Rs laying around, you’re going to need to find something else to do with those instead.

Thanks to [shinwachi] for the tip!

Syringe with diluted nail polish used to fill into cursive "FuzzyLogic" letters extruded into a surface of a 3D-printed block of plastic, as a demonstration.

Brighten Up Your Prints With This Nail Polish Approach

March 14, 2022 by Arya Voronova 25 Comments

It’s not enough to 3D-print a part – there’s a myriad of things you can do from there! [FuzzyLogic] shows us his approach of adding inlay labels, icons and text to a 3D print, by extruding them into the print and filling the resulting cavity with nail polish! This makes for colorful and useful prints, as opposed to dull single-color parts we typically end up with.

The devil’s in the details, and [FuzzyLogic] has got the details down to a technique. Nail polish has to be diluted with acetone so that it flows well, and a particular combination of syringe and needle will be your friend here. Of course, don’t forget to factor surface tension in – even with well-diluted nail polish, you cannot make the grooves too thin. A bit more acetone on a q-tip helps in case of any happy little accidents, and a coat of clear acrylic spray paint seals the lettering firmly in place. The five-minute video tells you all about these things and a quite few more, like the basics of extruding text and icons in a typical CAD package, and has a bit of bonus footage to those watching until the end.

Adding markings to our prints is a lovely finishing touch! If you’re looking for more of that, here’s a custom tool-changing printer with a pen attachment making beautiful custom enclosures for the Pocket Operator.

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Cheap Alternative Solvents For PCB Cleaning

April 29, 2020 by Dan Maloney 82 Comments

If you’re in the habit of using isopropyl alcohol to clean your PCBs after soldering, you probably have a nice big jug of the stuff stashed away. If you don’t, you’re probably out of luck, since the COVID-19 pandemic has pretty much cleared IPA out of the retail market. But don’t fret: depending on where you live, alternative PCB cleaning solutions may be as close as your nearest auto parts store.

[Steven]’s search for a cheaper and perhaps more readily available substitute for his usual dedicated flux cleaner lead him to try automotive brake cleaner on a few test boards. He suspected that they might contain acetone, which is prone to yield unfortunate results with solder resist and silkscreen on PCBs, so some tests were in order. The brand he tried was Normfest Bremsenreiniger MC-1, a German brand that according to its Safety Data Sheet contains only hydrocarbons like alkanes, butane, and propane. It did a fine job cleaning all but the crustiest rosin flux without collateral damage.

In the video below, [Steven] goes through a few more brands with similar results, and we were encouraged enough by his results to check brake cleaners made for the US market. Alas, almost all of the cheap and readily available aerosols have acetone as the principle ingredient, mixed in with methanol, ethanol, and assorted ingredients that together will probably make for a bad day. About the only US-sold brand without acetone that we could find was Keller-Heartt, which lists only naptha and ethanol on its SDS. There may be others, but make sure you test whatever you find.

Aerosol solvents aren’t the only way to clean a PCB, of course. Ultrasonic cleaners do a great job, and as [Steven] discovered, they’re generally safe for most components.

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