Reflowing With A Hair Straightener

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Around here, reflow ovens usually mean a toaster oven, and if you’re exceptionally cool, a thermistor and PID controller. There are, of course, a thousand ways to turn solder paste into a solid connection and [Saar] might have found the cheapest way yet: a hair straightener with a street value of just £15.

We don’t expect the majority of the Hackaday demographic to know much about hair straighteners, but [Saar] has done all the work and came up with a list of what makes a good one. Floating plates are a must to keep the PCB in contact with the heating element at all times, and temperature control is essential. [Saar] ended up with a Remington S3500 Ceramic Straight 230 Hair Straightener, although a trip to any big box store should yield a straightener that would work just as well.

One modification [Saar] added was a strip of Kapton tape to one of the ceramic heating elements. It’s not a replacement for a toaster oven or real reflow oven, but for small boards it works just as well.

Video below.

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Smart Reflow Oven is Over-Engineered

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[Linas] reverse engineered an AMOLED HTC 800×480 screen and interfaced it with an STM32 micro-controller, along with some other components, to make a gorgeously over engineered reflow oven.

Under the hood there is a PSoC5LP PID controller to control the 800W IR heating coil and two K-type thermocouples for sensing.

The real beauty is in the relatively small STM32 chip powering the HTC AMOLED screen. The AMOLED screen is high contrast and has a wide viewing angle, giving it a clear crisp view from all front facing viewpoints. Though pushing the limits of what the STM32F429i can do, [Linas] managed to make a very nice “home-grown” user interface, complete with user configurable settings and current temperature graphs.

The user interface looks very responsive and using some clever programming, [Linas] was able to make use of the potential of the screen to provide beautiful plots and interface widgets.

[Linas] goes into quite a bit of detail about the programming involved with rendering to the screen, so be sure to check out the video after the jump.

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Low-Power SMD Fireflies

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[Tyson's] family went with creating rather than buying Christmas presents last month, which gave him the opportunity to build some electronic fireflies for gifts. He drew inspiration from a similar firefly project we featured last year, but expanded on the original model by designing dedicated PCBs and housings for each of his firefly pieces.

Although he’d settled on using ATTiny85’s for this project, [Tyson] was fresh out of through-hole versions. He decided to skip the prototyping phase and go right for fabrication, cranking up the laser-jet printer for some toner-transfer, which successfully produced 4 functioning boards (and 3 failures). The fireflies were [Tyson's] first attempt at SMD soldering, and we’d have to say it’s a job well done; he reflowed each board with a cheap-o heatgun from Harbor Freight.

After some hiccups with fuse programming, [Tyson] got the code uploaded and the fireflies illuminated.  Swing by his site for the nuts and bolts on construction, then snag the project files here. (Direct .zip download)

A FPGA Controlled Reflow Oven

FPGA Reflow Oven

For Christmas, [Hamster]‘s wife gave him a mini-oven. Later that day, he tore it apart and built this FPGA controlled reflow oven.

We’ve seen plenty of reflow oven builds in the past. Most of those projects use a microcontroller to do closed loop control, sensing the temperature and toggling the heating element to hit a set point. This build uses the Papilo One FPGA development board as a controller. It implements a state machine that meets the reflow profile of the solder paste, ensuring SMD components are soldered properly.

The oven uses a MAX31855 to read temperature from a thermocouple. This device provides amplification, cold junction compensation, and analog to digital conversion which spits out the temperature over SPI. To control the heater, a 40A solid state relay is used.

The VHDL code that drives this oven is linked in the writeup, and has some interesting bits for those looking to experiment with FPGAs. It includes an SPI interface, display driver, and the temperature state machine logic.

Adding a SIM card to the Photon Q 4G LTE

[Charles] is a big fan of phones that have physical keyboards. He thinks they are better suited for writing lengthy emails, but unfortunately his HTC Desire Z was getting old so he had to replace it. [Charles] therefore decided to import the Motorola Photon Q from the USA which exposed one major problem. The Verizon phone uses CDMA so there is nowhere to put a GSM SIM. But a bit of hacking allowed him to add a SIM card slot to it. Even though he’s not the one who originally found this hack (XDA thread here), his write-up is definitely an interesting read. To perform this modification, he needed a hot air reflow station, a soldering iron, a Dremel with the appropriate cutting wheel and several SIM card slot assemblies from the Galaxy S3 (as the first ones usually get burned during the disassembly process).

Obviously the first steps involved opening the phone, which may have taken a while. Using hot air, [Charles] removed the EMI shield covering the SIM card IC . He then extracted the latter using the same technique. Finally, he removed another EMI shield covering the contacts to which the SIM card slot should be connected. A few minutes/hours of delicate soldering and case modding later, [Charles] could use his SIM card on his brand new phone.

Electric skillet reflow soldering guide

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It’s no secret that we’re bizarrely drawn to macro videos showing solder paste during the reflow process. This electric skillet reflow guide provides the fix we’ve been jonesin’ for while including some helpful tips for first-timers and veterans alike. Not sure what we’re talking about? Look at the grey paste at the top of this image. As it heats up it’s drawn under each component as seen in the lower half of the image.

This particular guide is aimed at one-off assembly so a solder paste stencil is not used (we learned a lot about those earlier in the month). It instead uses the painstaking toothpick application technique. It takes time but the upside is that once you get the hang of it you’ll apply the perfect amount of solder each time. After placing all of the components [Count Spicy] carefully transfers the board to an electric skillet, covers it with the glass lid (so he can see what’s going on), and sets the temperature just above the solder’s specified melting point.

Since the skillet is cheap and easy to find you really just have to order the solder paste to get into this type of assembly. Our only gripe is that you can’t really follow a temperature profile with this rig. For that you need to move up to some PID controlled hardware.

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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.

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