Almost Fail of The Week: Doing Surface Mount Reflow Wrong In Every Possible Way and Still Succeeding

Sometimes the best way to learn is from the success of others. Sometimes failure is the best teacher. In this case we are learning from [Tim Trzepacz]’s successive failures in his attempt to solder one board to another using a reflow oven. They somehow cancelled each other out, and he ended up with a working board. For those of you who have used a reflow oven, there will be eye rolling.

[Tim]’s first mistake was to use regular solder instead of paste. We can see how he got there logically; if you hand solder an SMD you melt solder onto the pads first to make it easier. However, the result was that he had two boards that wouldn’t sit flat on each other thanks to the globs of solder on the pads.

Not to be deterred, he laid the boards on top of each other and warmed up the oven to a toasty 650 degrees. Well, not quite. The dang oven didn’t turn to eleven, so he figured 500 would probably work too. Missing the hint entirely, he let his board bake in a nearly 1000F oven until he noticed some smoke which, he intuitively knew, definitely shouldn’t be happening.

The board was blackening, the solder mask was literally bubbling off the substrate, people were coming over to see the show, and he decided success was still possible. He clamped the heated boards together with a binder clip until they cooled. Someone gave him a lesson on reflow, presumably listened to through reddening ears.

Ashamed and defeated, he went home. However, there was a question in his mind. Sure it looks bad, but is it possible that the board actually works? After a quick test, the answer was yes. It loaded some code and an time later he was happily hacking away. Go figure.

3D Printering: Pastestruders


While bits of plastic are the usual material for 3D printers, there are hundreds of other materials that are equally well suited for 3D printing. One of the most famous is chocolate, a material so popular and easy to manipulate inside an extruder there are even Kickstarters for 3D printed chocolate bars.

teapotThere are many more materials deserving of being 3D printed, though: wax for lost wax castings, other foodstuffs for improbably shaped edibles, and ceramics so I can finally print a life-sized, functional version of the Utah Teapot.

Unfortunately, for all the progress of plastic extrusion, little has been done about extruding pastes, foods, and clay with a 3D printer. The RepRap paste extrusion working group is fairly close to being dead, so let this volume of 3D Printering explore what has been done in the world of paste printing.

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Type4me is a hardware clipboard for your digital copy and paste needs


It doesn’t happen often, but every now and again we find ourselves wanting for a more extensible cut and paste experience. Most notably we’ve searched for something that makes is very easy to keep multiple things in the clipboard and paste them as needed. Although we’ve tried several software offerings nothing really made it up to grade, but this hardware clipboard looks very promising. [Luca Dentella] calls it Type4me as it functions as a USB keyboard.

The PIC 18F14K50 enumerates as a USB keyboard, allowing it to send characters anywhere the cursor is located. It sends whatever string is stored inside, with an optional return character at the end. In addition to its keyboard properties it also establishes a serial connection, which allows you to push new strings to the device. This setup does require you to do copy or type your strings into a serial terminal, along with one of four special commands which are parsed by the microcontroller. One of these commands allows you to save the string to EEPROM so that it will be persistent through a power cycle.

The pasting back to the computer takes a mere push of the button. We’ve embedded the video demo after the break. It’s in Italian but there are English subtitles. Near the end [Luca] shows off the device as a macro button for gaming.

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Vapor phase reflow soldering

Ditch that old toaster oven and move to the next level of surface mount soldering with this vapor phase reflow method. [Ing.Büro R.Tschaggelar] put together this apparatus to use vapor phase reflow at his bench instead of sending out his smaller projects for assembly. It uses the heating element from an electric tea kettle to boil Galden HT 230 inside of a Pyrex beaker. There’s a copper heat break part way up the beaker to condense the chemical and keep it from escaping. When a populated board is lowered into the heated chamber, the solder paste reflows without the need to stress the components with unnecessary heat. Better than traditional reflow? At this level it’s hard to say, but we do find his method quite interesting.

[Thanks Chris]

Solder Paste How-to Tutorial

The application of Solder Paste is an essential part of short run manufacturing and prototyping. After getting back bare boards from a PCB shop, its time to get down to business and populate those boards. This new tutorial set assumes you have access to things such as stencils for your boards, but does mention a couple of resources on commercially available ways to purchase stencils. Of course, if you have a laser cutter, we can help you out. After getting your solder paste chops down, make sure you check out our guide to toaster oven reflowing.

[Thanks to P. Torrone]

Flux paste applicator gun

[Luciano] didn’t want to drop a lot of cash into a flux and solder paste applicator so he built his own for about $5. He re-purposed a hot glue gun which you can usually find at a dollar store. After removing the heating element he inserted the body of a syringe. The plunger has been modified to use a knitting needle inside of some plastic tubing. After taking the picture above he made an improvement by adding a milliliter scale to the plunger, allowing you to meter out the paste and also gauge how much remains.