Fluxlamp -- DIY Soldering Reflow Oven Project

[natester]

Hi all, I thought the eevblog community might be interested in a new project I've been working on. It's a WiFi-enabled, hackable soldering reflow oven. This is my first PCB design (I'm a software engineer by training) and I used KiCad 5 to design it.

I talk more about why I decided to make this and have a full build guide for the soldering reflow oven on my blog: https://nathan.vertile.com/blog/2019/04/24/fluxlamp-the-soldering-reflow-over-for-hackers/ and a bit about the electronics design: https://nathan.vertile.com/blog/2019/04/07/vertile-powercore/

I'm also looking for some beta testers and reviewers if anyone is interested in trying it out, please let me know! Just to set expectations, there are not that many available, since I've only made a few (by hand).

The project has already been certified by Arrow and will launch on Indiegogo if there is enough interest. If you're interested, please let me know by filling out this form: https://goo.gl/forms/NL6RoZNbVZ8R6ZUR2 and I'll email you when the campaign launches

[natester]

Since this was moved to the crowdfunding topic, I just want to point out this has not been crowdfunded, but if there is interest, it may be launched on Indiegogo.  Until then, it's just an interesting project I've been working on

[NorthGuy]

I have several construction lights exactly as the one you have used. If I remember correctly, they were expensive when I bought them. Thus I wouldn't consider re-using them for the owen. But this is an interesting non-conventional application for the construction lights.

[natester]

Thanks for the feedback! I was actually thinking the same thing, but it turns out these lamps are now about $15 on amazon (or were when I built mine, they're ~$17 now): https://amzn.to/2SRjqaD

Also since the lamp is kinda small, I was thinking of hooking it up to a toaster oven or some other heater. Just would need to be under 8amps or a bigger triac would need to be used

[PlainName]

That's a jolly clever idea! I would be interested in one of these (dependent, of course, on pricing). I currently use a toaster oven, with a homebrew controller, which this might be compatible with if it can use K-type probe input.

[spongle]

I get pretty decent results with a toaster oven using my Mk. 1 eyeball monitoring and super sophisticated phalange-actuated bang-bang control... have you demonstrated somewhere what real world improvement in outcome is given by your controller?

[natester]

Not sure exactly what you mean. I think you're saying you just manually control the toaster? (which is absolutely a valid option if it works well for you)

For me, being able to precisely control the temperature profile is important. Using hot air (what I did before this reflow oven) works fine for 1-offs, but having the consistency of a PID-controlled oven is nice for even a few boards. Also, my original motivation for this was that I was working on boards with BGA image sensors. Since I don't have an x-ray to inspect the solder joints after, I figure knowing that I can consistently hit the correct temperature profile should minimize issues with the solder joints.

[spongle]

But are you really hitting the correct reflow profile? Board temp is different than component temp is different than air temp.

Uniformly across the board? Hard to believe with that heating system.

Agree getting the same thing time after time is nice, but you can do that just by running the heater for a specific amount of time (or shutting off X seconds after you see reflow starting).

[natester]

That's a good question. Also, really hard to evaluate strictly quantitatively

Qualitatively, yes, I think the profile can be consistently hit. Some factors that make a difference are: ambient temp, amount the fluxlamp is cracked open, 40mm fan or no fan (optional, board has a mosfet installed and I've tested with both), PID controller tuning (defaults are pretty good), soldermask color (I noticed matte black is actually the most difficult since it absorbs so much heat, sometimes unevenly), location of the thermocouple (more important if no fan is used), thermocouple calibration (I've never done this, seems to work fine w/o).

There is a short shot of the profile in this video:



Of course realtime temp is being measured with the thermocouple, so this would need to be calibration & measured vs. board temp or/or avg oven temp to make sure it's correct, but that would be an offset from the profile temp, not variation along the profile over time. I also have a bolometric infrared sensor that can be wired to the Arduino (via headers on the PowerCore) that I was actually hoping to use to measure board temp. Still on my TODO list, and since these sensors are unfortunately quite expensive, I'm not sure if it's worth the cost.

Your comments have actually given me an idea though! I don't do this now, but since we have it, the actual temp profile (over time) could be logged and saved to a mobile app or web app, at the board level. This could both help refine the processes (detect problems when PIDs are out of tune, etc.) and catch/debug specific boards if there is a problem later, since we know exactly what happened during the reflow

[ebastler]

It's a neat idea, and I like the form factor of your little "lamp oven". But I wonder whether an IR radiation-based oven (which yours essentally is) is desirable at all?

My understanding is that -- even if you have good temperature sensing capability for closed-loop temperature control -- heat transfer by radiation will always be strongly dependent on the surfaces you irradiate. So black components will be heated much stronger than bright or reflective parts.

Isn't that why IR ovens have fallen out of fashion, and ovens which transfer heat via air convection or vapor phase condensation have become the norm? These modes of heat transfer are largely independent of the components' surface properties. (As is heat conduction through solid matter, e.g. in the frying-pan setup for homebrew use.)

The typical toaster-oven setups look more promising to me for home use. They still have some degree of radiative heating, in my understanding, but also a strong contribution from convective flow of hot air.

[natester]

Thanks for the feedback! Yep, size (making it compact) and low cost but effective were the key considerations for the FluxLamp, but I absolutely agree that having some other options such as a vapor phase condensation version would be fantastic. I guess I didn't explain this well above, but I was thinking of making the control board (I'm calling it the PowerCore available through a crowdfunding campaign. The idea is to enable folks to build things like the FluxLamp by providing software and build guides along with the control board, but BYO-lamp. To that end, it makes sense to explore how a vapor phase condensation reflow oven might work as well. I would think this will be much more expensive, but a "level up" option for those who want it.

One thing I was wondering about vapor phase condensation -- it seems like a good heat transfer dielectric medium with specific boiling temp is necessary. Does anyone know if something like Galden HT-230 is available or can be made in smaller quantities (and preferably from a local supplier like a big box retail store)? It would need to be equally safe & biologically inert. If the dielectric were available (for wayyy less than $1k), it would be reasonable to build a unit like https://hackaday.com/2010/10/15/vapor-phase-reflow-soldering/, controlled by the PowerCore .

[dasaki]

Sources:

https://github.com/dasaki/nanoReflowController

https://www.eevblog.com/forum/manufacture/could-this-be-the-smallest-and-cheapest-ir-reflow-oven/