Toaster oven for reflow

John Larkin wrote

Were there not markers that change color at a specific temperature?

Yes, little stick-on dots or crayons. But a sensor could measure or better yet control a time profile.

We have a little thermocouple gadget that rides the oven conveyer and logs temperature, to verify the profiles. The oven has 8 zones, and we have recipes for various products.

I looked up that model, and they are quartz.

Thanks for the info and the links.

Well with your manual control, your setup comes closest to the Spiess video. But it sounds a bit more complicated than he suggested. And it seems the placement of the thermocouple is critical to success.

After all the research, I wonder if the hotplate with an additional aluminum plate might be the best choice. It probably won't come close to the ideal heating profile, and heats from the bottom, which you would think is all wrong, but it appears to work, and from what the others say, is less likely to destroy stuff.

Peabody wrote in news:20181113-015017.293.0 @Peabody.us.newsgroupdirect.com:

IR absorption rate is not a function of color.

snipped-for-privacy@decadence.org says

Thanks for correcting me on that. So is there any difference in how well various electronics parts absorb IR?

size and/or mass makes a lot of difference.

First order answer: shiny metal is poor, everything else is the same.

Cheers

Phil Hobbs

Peabody wrote in news:20181118-003330.40.0 @Peabody.us.newsgroupdirect.com:

Typically they want to make devices which exhibit heat out of very emissive materials and usually if it is emissive, it is also receptive of IR energy.

So you will see matte finishes... usually.

Neon John wrote in news:hk73vdp7i7vf17qc466a8lrbugs00vvtgn@

Yep, and note how the item color has NOTHING to do with it.

The perfect example is water.

Oooops... try again.

They have a new one for $25 with an emissivity adjustment from 0.1 to 1.0. And a narrower angle. Made by Ames.

Ok, how about this:

The Oster single burner hotplate ($20 at Target) has a cast iron burner surface. Instead of having a controller, or trying to manually follow a profile, you buy two hot plates, set the temperature of one to 180C and the other to 220C (confirmed as stable temps by cheap-ass thermocouple meter).

After both are fully warmed up, put the board on the "soak" hot plate until it reaches soak temperature (confirmed by thermocouple) and for an additional two minutes, then move it to the "reflow" hot plate until it reflows. Then move it back to the soak hot plate for just a little while, then to a room temperature surface until it cools down.

Kinda like the fancy ovens with multiple zones.

Of course this depends on the Oster being able to maintain a temperature reasonably well.

Fundamentally, instead of trying to change the temperature in accordance with the profile, with controllers, solid state relays, ects., you fix the hot plate temps to the two critical temps in the profile - the soak temperature and the reflow temperature - and then measure the temperature of the board as it reaches soak temperature and set your timer for the appropriate soak time. The reflow part is pretty simple, based on observation. And then whatever works for cooling.

With a little experimentation, you might be able to convert all this to a simple time protocol - so much time on the soak hot plate, then so much time on the reflow hotplate, etc.

Anyone ever try doing it this way? Total cost would be under $50. No assembly required.

I like my ebay IR temperature meter very much, have put a piece of tape across the laser, do not like to look into laser reflections. Use brain when using it and it is OK.

The heater bars in a toaster oven are visibly incandescent, so the radiation probably peaks in the near IR, not "thermal" wavelengths. So the visible color of an object may matter.

The Planck peak occurs at

lambda = 2900 um*K / T

The peak of a 300K black body is therefore near 10 um. A heating element might be 1100K, putting its peak around 2.6 um. Visible dyes all crap out by 1 um.

(Messing around with an image-tube IR viewer is fun. Optics people get to play with cool toys.)

Cheers

Phil Hobbs

I have a Russian tube-based night vision thing, and a color CCD-based one that records movies too. Both have barely-human-visible IR illuminators, 850 maybe. Good for seeing what kind of critters skulk around at night.

Lots of regular cameras will respond to near IR, especially older ones with bad filtering.

I had one ancient Sony camera that worked fine as a viewer at 1050 nm.

I would expect the emissivity setting to have no effect whatever when the thermometer is aimed at a room-temperature target.