DIY SMT Solder Oven

Check the sparkfun webpage, I think they have worked out a PCB and design that works.

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Joe Leikhim K4SAT
"The RFI-EMI-GUY"©

"Treason doth never prosper: what\'s the reason?
For if it prosper, none dare call it treason."

"Follow The Money"  ;-P

Here's my thinking: Most of these cheap toaster ovens heat unevenly. Its possible that your sensor is reading in a cooler spot than where your PC board sits.

Also, make sure that the PC board is not exposed directly to the heating elements or direct radiation will heat it too fast.

One idea I've read about is to incorporate a small fan inside the oven to keep the air mixed and at a more uniform temperature. A small impeller on a long shaft with the motor sitting outside the oven will do.

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Paul Hovnanian     mailto:Paul@Hovnanian.com
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I'd certainly like to hear about your project, so please post your progress.

Put the TC on the metal of the heating element, if its on the PCB, you are experiencing overshoot because of the PCBs low thermal conductivity, perhaps?

Steve Roberts

This is the classic toaster-oven soldering guide:

The Sparkfun soldering ideas (here's a hotplate article, with links to the toaster project too):

Circuit Cellar article:

Another, from Cornell, with controller:

The articles above discuss the various problems, solutions, and results.

HTH, James Arthur

I use a waffle iron with dual sided grill plates. One side is for waffles and the other side is smooth for doing grilled cheese sandwiches (I'm guessing).

I use the smooth sides of the plates. I put spacers in, if needed, so the plates don't hit the components. This provides moderately even heating from below and above. Put a dab of solder paste in a visible area so you can see when the solder melts. Works fine for soldering those pesky ICs with exposed paddle.

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Mark

This guy recommends aluminum heat shields to spread the heat, avoiding hot spots and scorching:

"You will need to make the following modification to your toaster oven so that your boards don't get toasted by direct infra red radiation from the heating elements.

The objective is for the heater elements to simply heat the air inside the oven, so a direct line of infra red heat straight from the elements to the circuit board must be avoided.

The way to achieve this is to get some thin sheet aluminium and make a cut-out shape that just covers up the elements. You can use a disposable baking tray from the supermarket to make this aluminium shield."

Cheers, James Arthur

..and a couple more:

Un bel giorno Jacques St-Pierre digitò:

How do you manage the cooling phase? With homebuilt reflow ovens (made with toaster ovens, designed to keep the heat inside as much as they can) it is normally necessary to manually open the oven door at a certain point, in order to quickly dissipate the heat.

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emboliaschizoide.splinder.com

| > Steve Roberts | | This guy recommends aluminum heat shields to spread the | heat, avoiding hot spots and scorching: | |

| | "You will need to make the following modification to your toaster oven | so that your boards don't get toasted by direct infra red radiation from | the heating elements. | | The objective is for the heater elements to simply heat the air inside | the oven, so a direct line of infra red heat straight from the elements | to the circuit board must be avoided. | | The way to achieve this is to get some thin sheet aluminium and make a | cut-out shape that just covers up the elements. You can use a disposable | baking tray from the supermarket to make this aluminium shield." | | | Cheers, | James Arthur

This was my first thought, heat shields or diffusers.

Cheers

At this point, I did add a fan connect to back of the oven with 2 feet's of

3 inches metal pipe. The fan is located lower than the oven, so this prevent the heat from getting out by that opening. We also remove the bottom tray (normally use to remove crumb), this give an large opening to exit the heat when the fan turn on. We do not need to open the oven until the end of the process.

Bye Jacques

At this point, all my reading appear to agree with this. In my last test, I put a metal plate over the lower heater, this help. More modification will be require to install shielding on both heater.

I also put the heat sensor in the air near the PCB, instead of direct contact. This give more constant result.

I will try to install a fans inside the oven to move air around, this may help a lot. My first try was not successful, the fan I use was not moving air at all. I will try something else.

Bye Jacques

Hello, 12 inches by 12 inches is rather bigger than any toaster oven that i know of. This guy has custom built his own. Adjust your advice accordingly. That said, i do not get why the small overshoot from 245 C for RoHS solder to 250 C is damaging normal FR4. RTOP.

The man said his first unit had trouble with uneven heating. He further relates that the 2nd unit burns boards before it even gets to soldering temperature.

That also sounds like uneven heating and / or a direct IR path that burns the board before the more-reflective solder gets up to temperature.

ISTM 12x12 inches makes the likelihood of such problems even greater.

So the cure (if that's the culprit) is a heat shield that blocks the direct IR path.

Cheers, James Arthur