How to choose a thermocouple gas and bloating pain

##

Long time ago I used to use a toaster oven (TO) to cure epoxy mounts. The problem I experienced with TO’s was "Thermal Inertia". I know, no such thing. But wait a minute, there IS such a thing. The heating elements can heat up to 5000 degrees F. The TO runs the elements until it reaches a set temperature then switches off the current. Still, the element is quite hot and the temperature ramps way above the set temperature. Eventually it cools enough to where the temperature starts to fall. Here again you get thermal inertia. The temperature drops below a set point and the current comes on. But the element doesn’t immediately heat up. So the temperature continues to fall until the element heats up enough to overcome the downward fall of the temperature. It’s quite a thermal roller coaster inside a toaster oven.

They make and sell controllers that as you approach the set temperature the controller begins to modulate the power to the heating element, thus lowering the output before it gets to set temperature. Then it maintains a small current high enough to maintain the temperature. I looked into buying something like that but the cost back in the 90’s was prohibitive. Besides, I found that I could use an aluminum box with a 60 watt light bulb inside it to sufficiently warm and accelerate the cure of my epoxy mounts. Of course, a 60 watt light bulb is not going to reflow your solder, so something like an oven would likely be the way to go. Just be sure you know how high the temperature will soar above your set point. Maybe, for instance, if it exceeds your set temperature by 100 degrees F you could set your temperature 75 degrees F below your target. The oven will achieve reflow temps and go above by only 25 degrees. Certainly long enough to reflow your board.

Long time ago I used to use a toaster oven (TO) to cure epoxy mounts. The problem I experienced with TO’s was "Thermal Inertia". I know, no such thing. But wait a minute, there IS such a thing. The heating elements can heat up to 5000 degrees F. The TO runs the elements until it reaches a set temperature then switches off the current. Still, the element is quite hot and the temperature ramps way above the set temperature. Eventually it cools enough to where the temperature starts to fall. Here again you get thermal inertia. The temperature drops below a set point and the current comes on. But the element doesn’t immediately heat up. So the temperature continues to fall until the element heats up enough to overcome the downward fall of the temperature. It’s quite a thermal roller coaster inside a toaster oven.

They make and sell controllers that as you approach the set temperature the controller begins to modulate the power to the heating element, thus lowering the output before it gets to set temperature. Then it maintains a small current high enough to maintain the temperature. I looked into buying something like that but the cost back in the 90’s was prohibitive. Besides, I found that I could use an aluminum box with a 60 watt light bulb inside it to sufficiently warm and accelerate the cure of my epoxy mounts. Of course, a 60 watt light bulb is not going to reflow your solder, so something like an oven would likely be the way to go. Just be sure you know how high the temperature will soar above your set point. Maybe, for instance, if it exceeds your set temperature by 100 degrees F you could set your temperature 75 degrees F below your target. The oven will achieve reflow temps and go above by only 25 degrees. Certainly long enough to reflow your board.