Reflow soldering improved with carbon dioxide

co2_reflow-oven

This is exactly what it looks like. [Oleg] calls it soldering in inert atmosphere, but it’s just a toaster oven reflow hack dropped into a container full of carbon dioxide.

Why go to this trouble? It’s all about solder wetting. This is the ability of the molten solder paste to flow into all of the tinned areas of a board. [Oleg] talks about the shelf life of hot air leveled PCB tinning, which is about six months. After this the tin has oxidized. It will certainly not be as bad as bare copper would have, but it can lead to bad solder joints if your PCBs are more than about six months off the production line. This is one of the reasons to use solder flux. The acid eats away at the oxidized layer, exposing tin that will have better wetting.

But there is another way. Soldering in the absence of oxygen will also help the wetting process. CO2 is heavier than air, so placing the reflow oven in a plastic container will allow you to purge air from the space. CO2 canisters are cheap and easy to acquire. If you keg your own homebrew beer you already own one!

If you’ve got everything but the reflow oven just look around for a few examples of how to build your own.

BGA rework station

BGA

SMD components may be a little challenging for the home builder – even though the’re inordinately practical for homebrew PCBs – but if you play around with electronics and solder long enough, you’re eventually going to run into the horrors of BGA parts. Instead of convenient pins, BGA parts have tiny metallic balls on which solder is applied, a board is thrown through a reflow oven, and hopefully at the end, everything works. Sometimes these balls corrode or otherwise need to be reflowed. This isn’t an easy process, so [Edmar] came up with his own BGA rework station that costs much less than commercial offerings.

[Edmar]‘s build began when he wanted to repair a graphics card. A common error on his Amilo XI2428 graphics card is having the small balls on the underside of the chip corrode, leaving the user with a non-functional graphics card. Towel trick notwithstanding, the easiest way to fix this error is to heat up the card to above the melting point of solder, removing the chip, and resoldering it with careful application of solder paste.

[Edmar]‘s reflow station is made of an electric skillet for the bottom of the board, an infrared lamp for the top side of the board, and control circuitry constructed from an ATMega128, temperature sensors, and a huge power supply. The temperature is controlled via USB by a computer, allowing [Edmar] to set a temperature profile as recommended by the BGA chip’s data sheet.

Right now, removing a BGA chip works great, but [Edmar] is still working on the tech necessary to replace a BGA chip on a board.

How to repair a ribbon cable connection on consumer electronics

It’s not uncommon in cheaper devices to find a ribbon cable soldered directly to the circuit board like the one pictured above. Using a connector would have been a much more resilient approach, but adding parts adds cost. If you take a close look you’ll see things aren’t looking so great anymore. [Chaotic and Random] pulled this board out of his VW Camper Van. Rather than buy an expensive replacement part, he shows us how to repair a soldered ribbon wire connection.

This repair is rather invasive and he suggests trying some hot-air rework (possibly using a heat gun) to fix up any misbehaving connections. But if that has failed it’s time for the knife. The first step is to  cut the ribbon so that the LCD can be removed from the board. From there he peels the remaining scrap off ribbon of the pads. This makes us cringe as it could lift traces from the PCB, but he was gentle enough to avoid it. Now comes the time to start reassembling. After thoroughly cleaning the pads the ribbon is cut straight and resoldered. The trick is to flow the solder without melting the ribbon. He uses tin foil to cover the tip and cools it on a moist sponge just before reflowing solder.

It sounds like more art than science. But when the only alternative is to spend hundreds on a new part it may be worth a try.

More DIY solder flux

[GuShH] wrote a guide for making your own rosin-based solder flux. According to [Stephen] — who sent in the tip and tried this method himself — is works well, it’s cheap, but you will need to clean up a bit after using it on a PCB.

Only two ingredients are necessary to make your own liquid or paste flux: rosin and a solvent. The rosin being weighed in the image above, can be found from several sources. We looked in on the same method quite recently where flux was sourced from a music store. But [GuShH] suggests that if you can find some from a hardware store it is better because the music store variety tends to be ‘molten’ and doesn’t work quite as well.

Proportions are listed on his guide for light, medium, and heavy concoctions. He recommends isopropyl alcohol as the solvent, and has stored the flux in a clear dropper bottle. We’re fans of needle bottles and asked about sourcing them in a previous post (linked in the paragraph above) so check that comments section if you don’t know where to get one.

Grab your iron and add GameCube back to the Wii

One of the really cool things about the Nintendo Wii when it was first introduced was the ability to play GameCube games on it. This made it a no-brainer for a lot of folks to upgrade. But as the heyday of legacy systems fades into history, Nintendo decided this was no longer a selling point and stopped populating those components. The good new is, if you don’t mind a lot of PCB soldering you can add your GameCube bits to a modern Wii motherboard.

[Deadlyfoez] launched a raffle to raise enough money to buy a new version of the hardware (we guess the raffle prize is the modded console). He then proceeded to solder on four GameCube controller ports and a memory card reader. There are also a number of passive surface mount components that need to be added. But as the video after the break shows, once in place the functionality reappears on the software side.

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You might be a geeky dad if: your kids practice spelling in Morse code

Kids learn better if they’re engaged in the topic at hand. [Todd] found something that has his son just begging to practice his spelling words each night. He converts them all to Morse code and taps each out on the Morse code practice station they built together. To start off Todd connected the keyer to his Fluke 87 meter, using the continuity tester to sound a beep each time the key is depressed. But this is just a temporary setup until [Todd] could help guide his young one through some circuit design and assembly.

The replacement is based on a 555 timer. They grabbed an electronics project book and found the schematic along with a Morse code primer. With parts in hand [Todd] films as his son hones his soldering skills with each connection. The finished project uses the timer chip to produce the audio frequency heard from the on-board speaker. If you’ve never had the joy of teaching a kid how to solder, you’re going to love seeing the video.

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Homebrew solder pot is too dangerous even for us

[rue_mohr] is building a hexapod robot, and that meant he needed to tin a whole bunch of ribbon cables with solder. Using a soldering iron for this task would take far too long, so he built a homebrew solder pot to tin all those wires quickly. While [rue] was able to get solder on all those wires quickly, we need to question his method – he used a halogen light and reflector to melt all that solder.

The build began with a recycled halogen light fixture. After taking apart the entire assembly, [rue] reassembled it into something resembling a solder pot; a concave reflector and halogen light bulb sit perfectly flat on the table, ready to accept pieces of solder.

After throwing the switch and putting a few bits of solder in the reflector, the solder pot surprisingly worked. [rue] was able to quickly tin his ribbon cables, and the halogen bulb and reflector didn’t break yet.

This is one of the least safe solder pots we’ve ever seen – the bulb could easily explode, and melted solder could come pouring out of the reflector at any time. [rue] is aware of the safety implications and make sure to wear a pair of goggles. If it works though, we really can’t complain.

Check out the video of [rue]‘s solder pot (with an awesome temperature indicator light right in the middle of a pool of solder) in action after the break.

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